Specifications
| Parameter | Specification |
|---|---|
| Material | Ductile iron EN-GJS-500-7 / ASTM A536 65-45-12; ASTM A216 WCB variant for heavy gangs |
| Process | Water glass or silica sol lost wax investment casting, CNC turning, drilling and tapping |
| Tolerance | As-cast ISO 8062 CT7; bearing bore to H7, seal seat to h6, ISO 2768-m on non-critical features |
| Surface finish | Shot blast Sa 2.5, machined bore and seal seat Ra 1.6 um, exterior Ra 6.3-12.5 um |
| Weight range | 3.5 – 9.0 kg per piece |
| Heat treatment | Normalizing at 900 C or ferritizing anneal; WCB variant normalized and tempered to 156-207 HBW |
| Inspection | CMM report, bore gauge and air gauge verification, ultrasonic testing on load sections, hardness per ISO 6506 |
Key features
- Ferritic-pearlitic ductile iron EN-GJS-500-7 gives 500 MPa tensile with 7 percent elongation, tolerating the bending and shock loads of a disc gang in hard ground.
- Spheroidal graphite microstructure is verified per ISO 945 on every melt, with nodularity above 85 percent to guarantee ductility at the hub flange.
- Bearing bore machined to H7 with seal seat concentricity within 0.05 mm, extending bearing and lip seal life in abrasive dust.
- Cast-in grease cavity and relubrication boss allow a sealed-for-life or serviceable configuration without extra machined plugs.
- Raised bolt boss faces are machined in a single clamping, holding the disc mounting face flat within 0.10 mm to prevent disc wobble.
- Section thickness is graded from 14 mm at the hub barrel to 9 mm at the flange to remove dead weight while keeping fatigue strength above 200 MPa at 10 million cycles.
- Optional cast steel A216 WCB version raises impact capacity for offset and heavy-duty harrows working in rocky or virgin ground.
Applications
- Moreover, Mounted and trailed disc harrows for primary and secondary tillage
- Offset disc harrows and tandem gang assemblies
- Disc ploughs and disc ridgers
- Vertical tillage and high-speed shallow tillage tools
- Compact disc and stubble cultivator gangs
- Replacement hub service kits and aftermarket overhaul programs
Quality & compliance
Production runs under IATF 16949 process control with melt control, inoculant practice and pouring temperature recorded for every ladle. Where requested we submit PPAP documentation including control plan, PFMEA, process flow and initial process capability on the bearing bore and bolt circle. We issue material certification to EN-GJS-500-7 or ASTM A536 65-45-12 with chemical analysis, tensile results and graphite nodularity reports, and each heat is traceable from charge make-up to finished hub. Heat treatment charts covering normalizing or annealing cycles are archived per furnace load, full dimensional reporting accompanies every shipment, and coating options include black oxide, e-coat, epoxy primer and powder coat.
FAQ
Q1. Ductile iron or cast steel for a disc harrow hub?
Ductile iron EN-GJS-500-7 is the default choice because it damps gang vibration, machines cleanly and costs less than steel. We recommend the ASTM A216 WCB cast steel variant only where impact energy is extreme, for example offset harrows in rocky ground or high-speed vertical tillage tools.
Q2. How do you control bore accuracy for the bearing fit?
Hubs are rough turned, then finish bored on CNC lathes with a dedicated fixture that locates on the disc mounting face. Bores are verified with air gauging and CMM to confirm H7 size, roundness and concentricity to the seal seat, and results are included in the dimensional report.
Q3. Can you match an existing hub without drawings?
Yes. Send a sample hub and we will perform 3D scanning, produce a reverse-engineered model with a full dimensional report, and quote tooling for production. Minor design improvements such as added fillet radii or thicker wear lands are proposed before tooling starts.
Q4. Do you test for internal soundness?
Critical load sections are examined by ultrasonic testing, and sample castings are sectioned during development to confirm freedom from shrinkage in the barrel-to-flange junction. Moreover, any repair welding, where permitted, follows a qualified procedure and is documented on the part record.
Q5. What surface protection do you offer?
Standard is shot blast to Sa 2.5 with a rust-preventive primer. For longer field life we supply e-coat, two-component epoxy, powder coat or black oxide, with salt spray results documented per coating specification.
Q6. How do we start a project?
Send your drawing, sample or annual volume estimate to Wendy She at sales@cnsandcasting.com or WhatsApp +86-13777124360. We reply with material recommendation, tooling cost, sample schedule and tiered production pricing, usually within two working days.
