Double-sided GOES laser scribing changes the stress distribution, coating condition and thermal history of both faces. A matched-energy matrix shows whether the second pass earns its place through the final magnetic result. [1]
Keep two energy accounts
Record incident energy per scan length on each face and the pitch associated with it. The total across both faces and the exposure on each face answer different questions. If the first face receives the original single-sided exposure and the second receives the same again, the trial has doubled incident input. Any outcome cannot be attributed to symmetry alone.
Let E be an illustrative reference incident line energy in J/m. The following matrix uses relative exposure, not recommended production settings. It assumes comparable line pitch and beam definitions; otherwise the treated-area accounting must also change.
| State | First face | Second face | Purpose |
|---|---|---|---|
| Untreated | None | None | Matched material baseline |
| Single full exposure | E | None | Original single-sided response |
| Single half exposure | E/2 | None | Per-face exposure control |
| Double aligned | E/2 | E/2 | Equal total input, registered opposing tracks |
| Double offset | E/2 | E/2 | Same total input, changed track registration |
The half-exposure control matters because double-sided treatment at equal total input reduces each face’s exposure. A result different from the original single-sided state could reflect that reduction rather than an interaction between the faces.
Measure the proposed symmetry mechanism
Mark opposing track positions through a common sheet coordinate system. Nominal scanner alignment is not evidence that the two patterns coincide on the material. Inspect their offset and any change during handling or strip movement.
Where the hypothesis concerns reduced bending tendency, measure the final unloaded shape under a defined support condition. Where it concerns stress through thickness, select suitable depth-sensitive evidence. Equal face settings do not establish a symmetric residual-stress field, and a flat sheet does not prove that all magnetic or coating consequences are favourable.
Retain pass order, interval between passes and the material’s thermal condition. The second treatment encounters a changed sample. Reversing pass order or allowing a different cooling history can introduce a process variable even with identical energy totals.
Make surface integrity a face-specific result
Inspect both faces and preserve the location of relevant coating observations and electrical tests. A satisfactory averaged insulation result can leave a local treated area unresolved. Compare magnetic loss and excitation using identified paired specimens and the same test state.
For an independent comparison at the 23ZH90 catalogue point of 1.7 T, 50 Hz and ≤0.90 W/kg [2], assume total incident energy 100 J: either 100 J on one face or 50 J on each face. Fictional losses are 0.88 W/kg single-sided, 0.86 aligned double-sided and 0.89 offset double-sided on the same preparation/test basis. Assume expanded uncertainty of each paired difference is ±0.015 W/kg [3]. The aligned saving 0.020 has interval 0.005–0.035 W/kg; the offset change is unresolved. Carry the aligned option into face-specific coating and final-use qualification, retaining the half-exposure control. These results do not prove stress symmetry or transfer to another pass order.
Face identification, opposing-track registration, focus and surface coating state govern symmetry. Qualify both faces and do not infer a through-thickness stress pattern from matching visible line positions alone.
Show magnetic gains and coating tradeoffs beside the single-sided controls. Qualify the proposed two-face route with its matched matrix and final-use evidence; the primary studies support the treatment mechanisms, while this comparison establishes the chosen route.
References
- P. Rauscher et al., The influence of laser scribing on magnetic domain formation in grain oriented electrical steel visualized by directional neutron dark-field imaging, Scientific Reports 6, 38307, 2016, Table 1. DOI: 10.1038/srep38307.
- Nippon Steel Corporation, Grain-Oriented Electrical Steel Sheets, catalogue D004je, April 2020, specification and typical-property tables.
- B. N. Taylor and C. E. Kuyatt, NIST Technical Note 1297, Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, 1994, sections 5 and 6.