Custom Gray Iron Castings
Exceptional vibration damping, outstanding machinability, and highly cost-effective. We engineer premium flake graphite cast iron for heavy machinery, machine bases, and large counterweights.
Request a Free QuoteUnmatched Damping and Cost-Efficiency.
Characterized by its flake graphite microstructure, custom gray iron castings are the backbone of the heavy industrial sector. While it does not have the tensile strength of ductile iron, it excels in areas where rigidity, compressive strength, and vibration absorption are critical.
At Kurt Foundry, we specialize in pouring medium to massive gray iron components. Whether you require massive industrial counterweights, heavy flywheels, or custom hand wheels, our resin sand casting process ensures excellent surface finish, tight tolerances, and superior thermal conductivity at a highly economical price point.
View Material GradesCommon Gray Iron Casting Grades
Our metallurgy team carefully controls carbon and silicon equivalents to ensure the perfect flake structure. Below are the standard gray iron grades we cast.
| Standard / Grade | Min. Tensile Strength (MPa) | Typical Hardness (HB) | Common Applications |
|---|---|---|---|
| ASTM A48 Class 20 / 25 | ≥ 150 | 140 – 190 | Counterweights, non-pressure housings, hand wheels, light-duty covers. |
| ASTM A48 Class 30 | ≥ 207 | 170 – 220 | Flywheels, pump casings, gearboxes, machinery bases. |
| ASTM A48 Class 35 | ≥ 241 | 190 – 240 | Heavy machine tool beds, hydraulic cylinders, brake rotors. |
| ASTM A48 Class 40 | ≥ 276 | 200 – 260 | High-stress diesel engine blocks, heavy-duty flywheels. |
| DIN EN 1561 EN-GJL-250 | ≥ 250 | 180 – 230 | European equivalent for general engineering and machine parts. |
Our Gray Iron Sand Casting Process
Consistent quality starts with precise metallurgical control and superior mold making for large industrial parts.
1. DFM & Pattern Making
We analyze your CAD files for optimal castability, designing precise gating and risering systems to ensure dense, defect-free iron.
2. Resin Sand Molding
Ideal for heavy parts like counterweights and machine bases, our furan resin sand molds provide extreme rigidity and excellent surface finishes.
3. Melting & Inoculation
Scrap steel and pig iron are melted in medium-frequency induction furnaces. Careful inoculation refines the graphite flakes for uniform strength.
4. Thermal Analysis
Pre-pour spectrometry ensures the exact Carbon Equivalent (CE) required for the specific ASTM class of gray iron before pouring.
5. CNC Machining & QC
Capitalizing on gray iron’s excellent machinability, we fully CNC mill and turn the castings, verifying tolerances with CMM inspection.
What We Cast in Gray Iron
From providing massive stability to absorbing vibrations, gray iron is the material of choice for these components.
Heavy Counterweights
Leveraging the high density and cost-effectiveness of gray iron, we cast massive counterweights for elevators, cranes, tractors, and heavy construction equipment.
Industrial Flywheels
Because gray iron absorbs vibration significantly better than steel, it is the standard for large industrial flywheels, pulleys, and rigid power transmission components.
Custom Hand Wheels
Cast iron hand wheels offer excellent durability, structural integrity, and a solid grip for manual valve actuation and heavy machinery adjustments.
Why Partner with Us for Gray Iron?
We are specialists in heavy sand casting. Whether you need a batch of custom hand wheels or a massive tractor counterweight, our facility is equipped to handle the pour and the precision machining.
- Ideal for Large, Heavy Cross-Section Parts
- In-House 5-Axis CNC Machining Capabilities
- Strict Metallurgical Control & Spectrometry
- Seamless DDP/FOB Logistics to North America
Gray Iron Casting FAQs
Gray iron is generally more cost-effective than ductile iron. It possesses exceptional vibration damping properties (crucial for machine bases) and excellent thermal conductivity (great for motor housings). However, if your part needs to withstand high impact or requires flexibility, ductile iron is the better choice.
The graphite flakes inside gray iron act as a natural chip breaker and lubricant during the CNC machining process. This leads to much faster machining speeds, less tool wear, and a superb surface finish compared to casting steel.
Our heavy resin sand casting lines are equipped to handle custom gray iron components ranging from 50 lbs up to 5,000 lbs (2.5 tons) per single piece, making us an ideal partner for large industrial equipment manufacturers.
Welding gray iron is notoriously difficult due to its high carbon content and brittle nature, which can cause cracking during the heating and cooling cycle. We generally recommend redesigning assemblies to be bolted or cast as a single monolithic piece rather than welded.
Yes, Kurt Foundry provides fully integrated manufacturing. We cast the gray iron parts and utilize our in-house CNC machining centers to drill, mill, bore, and turn the castings so they are ready for immediate assembly upon delivery.
Ready to Quote Your Iron Casting Project?
Send us your 2D/3D CAD drawings. Our foundry engineers will provide a comprehensive DFM review and a competitive B2B quote within 48 hours.
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