astm a48 class 35 castings
Who this helps: Design Engineers / Buyers selecting gray/grey iron (ASTM A48) for housings, machine bases, pulleys, brake drums and other non-pressure parts where NVH damping, machinability and cost matter.
What you’ll get: a practical guide to ASTM A48 Class 35 castings—properties, microstructure, EN/ISO equivalents, process & CT notes, when to upgrade/downgrade, copy-paste drawing text, and links to deeper reads.
Prepared by YB Metal Solution. Share your drawing via /rfq—YB Metal will return a part-specific material choice, process window and test plan.
Author: YB Metal Solution Engineering Team (hereafter YB Metal)
Table of contents
- What Class 35 means (and doesn’t)
- Typical properties & microstructure (for designers)
- Standards cross-reference: ASTM ⇆ EN ⇆ ISO
- Where Class 35 works best (and where it struggles)
- Casting route, ISO 8062 CT & machinability notes
- Corrosion & NVH: coatings and damping advantages
- Alternatives: when to pick Class 40 / ductile / CGI / steel
- What to put on the drawing (copy–paste)
- What YB Metal delivers
- FAQs
What Class 35 means (and doesn’t)
Definition: In ASTM A48, “Class 35” means minimum tensile strength 35 ksi (≈241 MPa) measured on a separately cast test bar. The standard subordinates chemistry to tensile strength, i.e., composition is not fixed—meeting tensile is the requirement. ASTM International | ASTM+1
Implication: You can see different matrix balances (pearlite/ferrite) from different foundries and still meet Class 35. For wear, machining or hardness consistency, you may need to specify additional controls (e.g., Brinell range) or use EN/ISO grades that include hardness.
Leak-tightness: Flake graphite is not pressure-tight by nature. Class 35 is not a pressure-part material; consider ductile iron or impregnation + leak test if you must hold pressure (see internal links below).
Typical properties & microstructure (for designers)
Acceptance is by tensile per A48; values below are typical, for design context—not acceptance criteria.
| Property (typical) | Class 35 guidance |
|---|---|
| Tensile (Rm) | ≥ 35 ksi (241 MPa) (spec minimum) |
| Hardness (HBW) | ~ 170–220 HBW (typical range; not fixed by A48) |
| Modulus, E | 100–140 GPa (lower than steel → good damping) |
| Density | 7.1–7.2 g/cm³ |
| Thermal conductivity | high vs DI/steel → good heat dissipation |
| Microstructure | Type A graphite flakes, pearlite-leaning matrix common at this class |
| Machinability | Excellent—graphite lubricity, chip control |
Design cue: For NVH-sensitive housings, gray iron’s internal damping reduces ringing vs steel/ductile iron. See: Cast Iron for Noise & Vibration Damping
Standards cross-reference: ASTM ⇆ EN ⇆ ISO
| ASTM A48 | EN 1561 (EN-GJL) | ISO 185 | Notes |
|---|---|---|---|
| Class 35 | EN-GJL-250 | ISO 185 Grade 250 | Similar strength class; EN/ISO often also list hardness guidance. |
Cross-reference is approximate—confirm details in the target standard.
Standards referenced: ASTM A48 (gray iron, tensile-based classes) and EN 1561 / ISO 185 (grey cast irons by tensile grade; many users treat EN-GJL-250 as the closest peer to Class 35).
Where Class 35 works best (and where it struggles)
Best-fit parts (non-pressure, structural-light):
- Machine bases, motor/gear housings, pump frames (non-pressure)
- Brake drums, pulleys, flywheels, counterweights
- Compressor feet, general brackets with low impact risk
Use with caution / upgrade if:
- Pressure-tight is needed → shift to ductile iron (ASTM A536); see Selecting Iron for Pressure Parts
- High impact/shock → consider ductile iron or cast steel
- High wear at low sliding speed → consider pearlitic/harder gray (EN-GJL-300 / ASTM Class 40) or surface treatments
- High corrosion → use coatings or material upgrade (see §6)
Casting route, ISO 8062 CT & machinability notes
Process choice by geometry & surface:
- Green Sand Casting
- Resin vs Green Sand (accuracy/finish)
- Shell Molding for Thin-Wall
Dimensional control: call ISO 8062 CT per size band; see ISO 8062 Casting Tolerances
Machining: Gray iron machines easily, but mind graphite dust and edge crumble:
- Tooling & coolant strategy: Machinability: Gray vs Ductile Iron
- Surface targets by process: Surface Finish by Process (Ra)
Corrosion & NVH: coatings and damping advantages
- Corrosion: Gray iron rusts in outdoor/splash service—solve with coating stacks (zinc-rich epoxy + epoxy mid + PU top for C3/C4), prep Ra 6–12 µm after blast; see Coatings vs Material Choices
- Damping (why gray wins): Flake graphite breaks up vibration energy—great for NVH-sensitive housings; see Why Gray Iron Still Wins
Alternatives: when to pick Class 40 / ductile / CGI / steel
| Option | Why choose it | Trade-offs |
|---|---|---|
| ASTM A48 Class 40 / EN-GJL-300 | +10–20% strength; better wear | Harder to machine; slightly lower damping |
| Ductile iron (ASTM A536 65-45-12 / EN-GJS-450-10) | Pressure-tight, impact-tolerant | Damping ↓ vs gray; cost ↑ |
| CGI (ISO 16112 GJV-300/350) | Middle ground: strength ↑ & decent damping | Process window tighter; machining load ↑ |
| Cast steel (A27/A216) | High impact/shock, weldable | NVH poor; heavier machining |
| ADI (A897, e.g., 900–1400 MPa) | Strength/fatigue extreme with iron economics | Not a corrosion upgrade; machining load ↑ |
What to put on the drawing
Material call-out
Material: ASTM A48 Class 35 (gray iron). Acceptance by tensile on separately cast test bars per A48.
Optional: Brinell hardness (HBW) informational range 170–220, measured on casting.
Casting & dimensional
Process: [Green sand / Resin sand / Shell], supplier to propose for geometry.
Tolerances: ISO 8062 CT [grade] per size band; maintain machining stock on all critical faces.
Soundness: Supplier to design gating/risering to avoid shrinkage at T/Y/X junctions; provide plan at PPAP.
Coating (if outdoor/C3–C4)
- Prep: shot-blast to clean metal; blast profile Ra 6–12 µm (240–475 µin).
- Primer: zinc-rich epoxy 60–80 µm; Mid: high-build epoxy 80–120 µm; Top: aliphatic PU 40–60 µm.
- Mask: fits/threads/sealing faces (see view).
QA & documentation
Provide tensile test (Rm) per A48, metallographic graphite form/type snapshot on pilot, and CMM FAI on datum stack. If pressure-tested: shift to ductile iron or specify impregnation + leak test (method/limit) on drawing.
What YB Metal delivers
YBmetal Solution quotes with a material plan attached:
- Class 35 vs alternatives decision backed by section map, NVH and duty.
- Recommended process route (green/resin/shell), CT grade and machining stock.
- Coating stack (if outdoor) with DFT/cure & adhesion checks.
- Pilot evidence pack: tensile logs, hardness snapshots (if used), micrographs (graphite type), and CMM FAI.
Need a part-specific plan? Upload your drawing at /rfq—we’ll return recommendations and a quote.
FAQs
CTA — specify with proof, not guesses
Cut cycle time without burning inserts. Upload your drawing to /rfq—YB Metal will send cutting data, tool list, and a coolant/filtration plan tailored to your part.