gray iron grades ASTM A48 vs EN-GJL
Who this helps: Buyers and Design Engineers selecting gray/grey iron for housings, covers, manifolds, machine bases and brake/drum components.
What you’ll get: a clean ASTM A48 ↔ EN-GJL cross-reference, typical property windows, and quick selection notes you can use on drawings.
Prepared by YBmetal Solution. Share your drawing via /rfq—YB Metal will return a material recommendation with process notes and a quote.
Author: YB Metal Solution Engineering Team (hereafter YB Metal)
Table of contents
- What the two standards really mean
- Cross-reference table: ASTM A48 ↔ EN-GJL
- Typical properties & what drives them
- How to choose a grade in practice
- Notes for drawings: CT, Ra and stock
- What YB Metal delivers
- FAQs
What the two standards really mean
- ASTM A48 (Gray Iron Castings) class numbers are minimum tensile strength in ksi measured on a specified test bar (e.g., Class 30 = 30 ksi ≈ 207 MPa).
- EN 1561 (EN-GJL) uses minimum tensile strength in MPa (e.g., EN-GJL-250 = 250 MPa).
- Both are test-bar based minimums. Actual casting sections vary by wall thickness, cooling rate, graphite flake form and matrix (ferrite/pearlite). Use the table below as a practical mapping, not a legal equivalency.
Cross-reference table: ASTM A48 ↔ EN-GJL
Use these as typical pairings when you need an equivalent. If your part is thin-walled or very heavy-sectioned, verify with your supplier.
| ASTM A48 Class (min UTS) | Approx. MPa | Common EN-GJL Pairing (min UTS) | Where it’s used |
|---|---|---|---|
| Class 20 (20 ksi) | ~138 | EN-GJL-150 (150 MPa) | Large bases, vibration-damping housings where strength is secondary. |
| Class 25 (25 ksi) | ~172 | EN-GJL-150 / 200 | Covers, gearboxes, pump bodies with generous walls. |
| Class 30 (30 ksi) | ~207 | EN-GJL-200 | General housings, brackets, machine frames. |
| Class 35 (35 ksi) | ~241 | EN-GJL-250 | Housings/drums needing higher strength with good machinability. |
| Class 40 (40 ksi) | ~276 | EN-GJL-250 / 300 | Stiffer housings, flanges; moderate dynamic loads. |
| Class 45 (45 ksi) | ~310 | EN-GJL-300 | Higher strength gray iron; check section-size limits. |
| Class 50 (50 ksi) | ~345 | (Often transitions to ductile grades) | If you truly need ≥300 MPa in casting sections, consider ductile iron (EN-GJS / ASTM A536). |
Reminder: EN-GJL grades commonly used are 150 / 200 / 250 / 300. Some ASTM classes (e.g., 50) may not have a strict EN-GJL match in real casting sections.
Typical properties & what drives them
Values below are indicative windows for design screening. Actual data depends on section size, microstructure and melt control.
| Property | Lower-strength gray (A48-20/30; EN-GJL-150/200) | Higher-strength gray (A48-35/40/45; EN-GJL-250/300) | Notes |
|---|---|---|---|
| UTS (MPa) | ~150–220 | ~240–320 | Test-bar minimums per standard; thin sections trend higher. |
| Hardness HBW | ~150–210 | ~190–260 | Correlates with pearlite fraction; higher HB improves wear, raises tool wear. |
| Elastic modulus (GPa) | ~90–120 | ~110–140 | Lower than steel; good for vibration damping. |
| Elongation (%) | ~0.5–1.5 | ~0.5–1.0 | Flake graphite limits ductility. |
| Thermal conductivity (W/m·K) | ~36–55 | ~28–45 | Falls as pearlite and alloying increase. |
| Damping (qual.) | Excellent | Good–Very good | Gray/grey iron outperforms ductile steel in NVH. |
| Machinability | Excellent | Good | Free graphite lubricates; hardness drives tool life. |
What moves the numbers
- Graphite flakes: size, distribution and orientation dominate damping and machinability.
- Matrix: more pearlite → higher UTS/HB, lower thermal conductivity.
- Section size: thin walls cool faster → higher UTS/HB; heavy sections trend lower.
- Melt/inoculation: carbon equivalent (CE), inoculants (Si, Ca, Al, rare earths) control chill and flake form.
How to choose a grade in practice
Start with functional drivers
- NVH/damping priority → A48-30 / EN-GJL-200 or A48-35 / EN-GJL-250.
- Higher stiffness/strength without moving to ductile → A48-40/45 or EN-GJL-250/300 (confirm section size).
- Wear resistance on rubbing faces → push hardness via more pearlite (within machinability limits).
- Pressure-tight or high impact → consider ductile iron (EN-GJS / ASTM A536) instead of gray.
Design levers
- Keep wall thickness uniform; blend ribs to ≤ 60–70% of wall thickness; add generous radii.
- Set as-cast CT by size band (ISO 8062) and leave machining stock only where needed.
- Call out Ra (µm) by zone; gray iron can reach fine finishes after machining.
Helpful reads by your side
Notes for drawings: CT, Ra and stock
- Material call-out (example):
- “EN-GJL-250 (ASTM A48 Class 35 acceptable). Matrix pearlite ≥ 70% at critical faces.”
- As-cast tolerance: specify ISO 8062-3 CT per size band (e.g., CT8–CT10 typical for medium parts).
- Machining stock: faces/ODs +1.5–3.0 mm (0.06–0.12 in) as needed; bores by diameter band.
- Surface: sealing faces after machining Ra 1.6–3.2 µm; exterior cosmetic faces may be as-cast + shot-blast.
- Inspection: CMM/3D scan on datum scheme; hardness trend and microstructure snapshots on first articles.
FAQs
CTA — specify with proof, not guesses
Need help locking the grade and process for your part? Upload your drawing to /rfq—YB Metal will propose the material, CT band and machining stock that hit your targets.