SG 450/10 and SG 500/7 are two of the most commonly specified ductile iron grades in IS 1865. Their numbers look close, but their matrix structures differ, and so do the jobs they suit.
Reading the grade name
In IS 1865 grade names, the first number is the minimum tensile strength in MPa and the second is the minimum elongation in percent. So SG 450/10 means at least 450 MPa and 10% elongation, while SG 500/7 means at least 500 MPa and 7% elongation.
Typical properties
| Property | SG 450/10 | SG 500/7 |
|---|---|---|
| Tensile strength min | 450 MPa | 500 MPa |
| 0.2% proof stress min | 310 MPa | 320 MPa |
| Elongation min | 10% | 7% |
| Typical hardness | 160–210 HB | 170–230 HB |
| Matrix | Mostly ferritic | Ferritic-pearlitic |
| EN equivalent | EN-GJS-450-10 | EN-GJS-500-7 |
Values on separately cast test bars. Properties in the casting depend on section thickness.
Choose SG 450/10 when
- The part takes shock or impact, or must bend before it breaks.
- You need high elongation with more strength than SG 400/15.
- Machinability and consistent hardness matter. A ferritic matrix machines easily.
Choose SG 500/7 when
- The part needs more strength and wear resistance, and its impact loads are moderate.
- You want a general engineering grade for housings, hubs, brackets and gear blanks.
- Slightly higher hardness helps against wear or fretting at mating faces.
Tip: specify hardness range and test location on the drawing as well as the grade. It gives the foundry and your incoming inspection a clear, measurable target.
How the foundry hits the grade
The difference between these grades is mainly how much pearlite forms in the matrix. That depends on chemistry, alloying elements, inoculation and cooling rate. At Ferro Tech we confirm chemistry by spectrometer and CE analyser before pouring, then measure nodularity and the ferrite / pearlite ratio with micro image analysis on every heat. See our laboratory.
Not sure which grade fits? Send us your drawing and we will recommend one.