Scratches, pits and indentations on cast iron reference surfaces will break flatness, affect gauge fitting and lead to unstable measurement data. The repair process varies based on damage depth, including simple grinding finishing for shallow scratches and casting filling + precision scraping for deep pits.
1. Pre-repair preparation work
First, thoroughly clean the whole platform surface. Remove cutting fluid, oil, metal powder and rust with degreaser and wire brushes, then dry completely. Mark all scratches and pits with a marker and classify damage grades:
Shallow scratch: depth less than 0.03 mm, no concave sag
Medium scratch / small pit: depth 0.03–0.15 mm
Deep pit / heavy indentation: depth over 0.15 mm, obvious depression
Adjust all supporting feet to ensure the cast iron plate bears uniform force to avoid secondary deformation during repair. Cover the undamaged precision areas with protective tape to prevent accidental abrasion.
2. Repair for shallow fine scratches
Shallow abrasions only damage the surface scraping texture without forming depressions, suitable for manual grinding and re-scraping:
Use progressively finer abrasive stones (240# → 600# → 1200#) to polish scratch areas gently along a cross direction, eliminate raised burrs and uneven ridges caused by scratches.
Clean abrasive residue repeatedly to avoid embedding hard particles into cast iron pores.
Perform precision hand scraping on the polished zone to restore uniform blue contact points, matching the flatness of surrounding intact surfaces.
Inspect flatness with a straight edge and feeler gauge to confirm no local height difference.
3. Repair for medium pits and moderate indentations
For pits with slight depression that do not penetrate the plate body, adopt cast iron powder cold welding filling:
Grind the inner wall of pits to remove rust and oxide layers, create a rough bonding surface, then blow away all dust.
Mix cast iron repair adhesive with fine cast iron powder at a fixed ratio, fill the pit slightly higher than the original platform surface to reserve grinding allowance.
Leave it to fully cure at room temperature for 12–24 hours; avoid high temperature or vibration during solidification.
After curing, grind the filler flush with the base metal surface with abrasive stones, then carry out precision scraping to reconstruct the reference datum.
4. Repair for deep large pits and heavy impact indentations
Deep damage with large missing areas requires argon arc cold surfacing welding to ensure material consistency and structural stability:
Chisel and grind the pit to form a stepped groove, clear all rust, fatigue layers and microcracks around the damage. Preheat the local area slightly to reduce welding thermal stress.
Use cast iron special welding rod for low-current cold surfacing, control single welding bead width to prevent local overheating and platform deformation.
After welding, cool naturally without forced water cooling to avoid new residual stress. Grind the welding protrusions flat once cooled.
Conduct full-area precision scraping on the repaired zone, and use a level instrument to check overall flatness, readjust supports if slight warpage occurs.
5. Post-repair maintenance and precision protection
Wipe the repaired surface with anti-rust oil to block air and cutting fluid, preventing rust recurrence on the filler or welding zone.
Avoid placing sharp, heavy workpieces directly on the repaired area within 72 hours to prevent secondary scratch and indentation.
Re-calibrate the whole cast iron platform every 3 months after repair to track flatness change of the repaired position.
References
GB/T 7714
Xu W, Jiang L. Surface defect repairing technology of cast iron inspection platform[J]. Equipment Manufacturing Technology, 2020(7): 156-159.
MLA
Xu, Wei, and Lei Jiang. "Surface Defect Repairing Technology of Cast Iron Inspection Platform." Equipment Manufacturing Technology, vol. 7, 2020, pp. 156-159.
APA 7th
Xu, W., & Jiang, L. (2020). Surface defect repairing technology of cast iron inspection platform. Equipment Manufacturing Technology, 7, 156–159.
