1. Introduction
Spheroidal graphite cast iron 600/3(BS EN 1563:1997), also known as ductile cast iron, has significantly altered the landscape of cast metals by offering an ideal balance between strength, ductility, and cost-effectiveness.
Its unique microstructure, defined by nodular graphite embedded in a metallic matrix, imparts superior mechanical characteristics compared to traditional gray or malleable cast irons.
The designation SG Cast Iron 600/3, according to BS EN 1563:1997, specifies a material with a minimum tensile strength of 600 MPa and minimum elongation of 3%,
situating it as a robust option for applications demanding both strength and moderate plasticity.
This grade bridges the mechanical gap between conventional cast irons and low- to medium-carbon steels, offering design engineers a compelling alternative where weight reduction, castability, and performance intersect.
2. Material Composition and Microstructure
To understand SG Cast Iron 600/3’s mechanical prowess, one must begin with its metallurgical fundamentals.
The alloy’s performance stems from the intentional formation of spheroidal graphite nodules, achieved through precise magnesium treatment.
The rounded shape of the nodules creates fewer stress points than the flat graphite flakes found in grey iron; this inhibits the creation of cracks and provides enhanced ductility.
This nodular graphite structure inhibits the creation of linear cracks, hence the ability to withstand distortion.
Typical Chemical Composition of spheroidal iron 600/3：
| Element | Typical Range (% by weight) | Function / Role |
|---|---|---|
| Carbon (C) | 3.4 – 3.8 | Forms graphite nodules; provides castability and thermal conductivity |
| Silicon (Si) | 2.2 – 2.8 | Promotes graphitization; strengthens ferrite; controls carbide formation |
| Manganese (Mn) | 0.1 – 0.5 | Strengthens pearlite matrix; too much can promote carbide or reduce ductility |
| Magnesium (Mg) | 0.03 – 0.05 | Key nodulizing agent; converts graphite flakes to spheroidal form |
| Phosphorus (P) | ≤ 0.05 | Kept low to avoid embrittlement and excessive shrinkage |
| Sulfur (S) | ≤ 0.02 | Must be minimized; reacts negatively with magnesium and promotes flake graphite |
| Copper (Cu) | 0.1 – 0.5 (optional) | Can enhance tensile strength and pearlite formation |
| Nickel (Ni) | 0.0 – 0.5 (optional) | Improves toughness and corrosion resistance (if used) |
| Chromium (Cr) | ≤ 0.1 | Sometimes used in small quantities for wear resistance, but can increase hardness |
Notes:
- The exact composition may vary slightly depending on foundry practices, heat treatment intentions, and specific application requirements.
- Control of Mg, S, and nodularization treatment is crucial for ensuring the correct nodularity and resulting mechanical properties.
The matrix in 600/3 is generally a combination of ferrite and pearlite, with ferrite improving ductility and pearlite contributing to strength and hardness.
The nodularity typically exceeds 80%, and nodule count often surpasses 100 nodules/mm², both being critical for achieving the intended mechanical properties.
Comparatively, SG 600/3 offers 3–5 times higher toughness than gray iron, and roughly 80% of the strength of quenched and tempered steels such as AISI 1045, yet at a lower cost and with better castability.
3. Mechanical and Physical Properties
Spheroidal iron 600/3’s mechanical properties allow it to perform under dynamic, impact, and structural loading, making it a prime choice for components exposed to cyclic stress.
Mechanical Properties:
| Property | Value Range |
|---|---|
| Tensile Strength (UTS) | ≥ 600 MPa |
| Yield Strength (0.2% offset) | ~ 400 MPa |
| Elongation (A₅₀) | ≥ 3% |
| Brinell Hardness (HB) | 170 – 230 |
| Fatigue Strength (Rotating) | ~ 300 MPa |
| Impact Energy (Charpy @ RT) | 7 – 12 J |
Physical Properties:
| Property | Value |
|---|---|
| Density | ~ 7.1 g/cm³ |
| Thermal Conductivity | 40–50 W/m·K at 200 °C |
| Specific Heat | ~ 460 J/kg·K |
| Damping Capacity | ~ 25–30% higher than steels |
| Shrinkage Allowance | 1.0–1.2% (linear) |
4. Casting Suitability for SG Cast Iron 600/3
SG Cast Iron 600/3 demonstrates excellent casting characteristics due to its balanced fluidity, moderate shrinkage behavior, and high dimensional stability.
These qualities make it well-suited for a wide variety of medium-to-high complexity components where strength and fatigue resistance are critical.
Key suitability attributes:
- Good Fluidity: Enables filling of intricate mold geometries and thin-wall sections (>5 mm), especially when silicon content is optimized (~2.5–2.8%).
- Moderate Shrinkage (~1.0–1.2%): Can be effectively compensated through pattern allowances and riser design, enabling precise dimensional control.
- Low Hot Cracking Tendency: The spheroidal graphite structure reduces internal stress concentrations during solidification.
- Excellent Weldability (in cast state): Although not as ductile as lower-grade SG irons, 600/3 is still weld-repairable with suitable preheat and post-weld treatment.
- Adaptability to Heat Treatment: Properties can be enhanced via normalizing or stress-relieving processes to tailor hardness, strength, and toughness.
5. Applications and Performance in Use
SG 600/3’s strength and vibration-damping capacity make it indispensable across high-load, fatigue-sensitive applications.
Several industries deploy this grade in mission-critical components:
- Automotive: Crankshafts, control arms, differential housings, engine brackets
- Municipal Infrastructure: Pressure-tight manhole covers, fittings, water and sewer pipe junctions
- Construction and Agriculture: Gearbox housings, pump bodies, plow assemblies
- Wind Power and Marine: Rotor hubs, base plates, flanges, ballast components
In automotive control arms, for instance, fatigue testing reveals SG 600/3 can endure stress ranges of ±250 MPa for over 2×10⁷ cycles,
meeting performance metrics close to quenched and tempered steels, but at significantly reduced cost and processing complexity.
6. Advantages and Limitations
Advantages:
- Superior fatigue and impact resistance compared to gray iron
- Excellent castability, supporting intricate geometries
- Reduced weight-to-strength ratio, ideal for dynamic applications
- Good machinability, lowering secondary processing costs
- High damping capacity, mitigating resonance and wear
Limitations:
- Lower elongation (3%) than softer SG grades (e.g., 400/15)
- Carbide formation risk if cooling is uncontrolled or over-inoculated
- Temperature sensitivity—exposure >400 °C may degrade mechanical properties over time
7. Compliance with Global Standards
SG Iron 600/3 corresponds to different equivalents in other standards:
- ISO 1083: EN-GJS-600-3
- ASTM A536: Grade 80-55-06 (close equivalent, depending on elongation target)
- DIN 1693: GGG 60
- JIS G5502: FCD600
8. Comparison with Other SG Iron Grades
| Grade | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Hardness (HBW) | Typical Microstructure |
|---|---|---|---|---|---|
| SG 400/15 | ≥400 | ~250 | ≥15 | 130–180 | Ferritic |
| SG 500/7 | ≥500 | ~320 | ≥7 | 150–200 | Ferritic-Pearlitic |
| SG 600/3 | ≥600 | ~400 | ≥3 | 170–230 | Pearlitic-Ferritic |
| SG 700/2 | ≥700 | ~500 | ≥2 | 200–270 | Predominantly Pearlitic |
| SG 800/2 | ≥800 | ~600 | ≥2 | 230–300 | Fully Pearlitic |
| SG 420/12 | ≥420 | ~260 | ≥12 | 140–180 | Ferritic (improved ductility) |
9. Conclusion
Spheroidal Graphite Cast Iron 600/3 stands as a hallmark material in modern casting engineering.
With its a combination of high strength, good ductility, superior fatigue resistance, and excellent castability.
It offers an optimal solution for engineers and manufacturers seeking reliable performance without the cost or complexity of alloy steels.
LangHe is the perfect choice for your manufacturing needs if you need high-quality SG Cast Iron 600/3 castings.
