An edge repair can remove a conductive burr while also removing sound steel, disturbing the original coating or changing joint geometry. The inspection should record both the defect removed and the additional region changed. A smooth final edge answers only part of the repair question.
Define the permitted repair through responsible engineering and a qualified procedure. When the original defect, affected layers or design clearances are uncertain, that uncertainty belongs in the disposition before any work begins.
Preserve the original cross-section
Map the abnormal feature relative to a repeatable datum. Record relevant sheet identity, edge position, joint geometry and coating condition. Use a measurement method capable of resolving the change the repair is expected to introduce.
An original photograph without a scale or datum may show the feature but not support a material-removal comparison. Retain geometric observations suited to the actual edge, including access limits where several layers overlap.
Define the removal boundary
After the approved repair, compare the same section or profile with the original record. Identify steel removed beyond the abnormal projection and the newly exposed or disturbed coating region. Do not assign a universal harmless removal width.
Define the electrical boundary
Evaluate whether the conductive path has been removed under the relevant contact state. The repaired edge may remain close enough to another layer or structure to create an alternative connection. A free-state inspection and an assembled-state check can address different conditions.
Define the magnetic and fit boundary
Check whether the changed edge belongs to a joint, envelope or other magnetically sensitive region. The geometry and design determine which dimensional and magnetic comparisons are necessary. Removing a feature from a nonfunctional projection is a different case from altering an overlap.
Inspect the newly affected surfaces
Repair may create residue, debris, coating discontinuities or a changed surface state. The qualified process should address their disposition and the verification appropriate to the material system. Applying an unqualified surface treatment can introduce another problem while concealing the visible one.
Keep electrical tests specific to the interface affected. A core-ground isolation result does not automatically demonstrate that adjacent laminations are isolated. Similarly, aggregate magnetic performance may not resolve a small local contact source.
Relate the benefit to the added change
The repair record should contain the original defect, removed section, remaining geometry, coating boundary and post-repair functional evidence. It should state which layer regions remain unobserved. This makes the decision reproducible if another reviewer or receiving factory examines the packet later.
A successful repair demonstrates that the targeted problem is removed without an unacceptable new change. The absence of a visible burr is evidence for that narrow feature; the dimensional, electrical and magnetic comparisons establish whether the repair restored the packet’s required function.
Account for steel removed beyond the burr
For 23ZH90, use 0.23 mm nominal thickness and catalogue assumed density 7,650 kg/m³ [1]. Assume an approved repair removes 0.50 mm of sound edge over 100 mm on each of 20 sheets, excluding the burr itself. Added removed volume is 0.50 × 100 × 0.23 × 20 = 230 mm³, corresponding to 1.760 g of steel. An assumed 0.20 mm sound-edge removal allowance would permit only 92 mm³ for that geometry, so the proposed repair exceeds it by 138 mm³. Retain before/after profiles and uncertainty [2], then obtain engineering disposition for the joint and fit consequences; small removed mass is not a magnetic acceptance argument.
Manufacturing controls. Burr formation, cut-edge position, joint overlap and the approved repair depth determine how much healthy material changes. Control residue, new coating damage and alternative bridges alongside the repaired contour.
References
- Nippon Steel Corporation, Grain-Oriented Electrical Steel Sheets, catalogue D004je_03_202004, 2020, Specifications; Size and Form Tolerances.
- JCGM, JCGM 100:2008, Evaluation of measurement data — Guide to the expression of uncertainty in measurement, 2008.