塗膜電磁鋼片退火附著性之研究：氣密爐退火的爐氛與底材效應

Investigations on the Post-Annealing Adhesion Capability of Coated Electrical Steels Annealed in the Air-tight Furnace: Effects of Furnace Atmosphere and Substrate

電磁鋼片（Electrical steels, ES）是具有特殊電磁特性的鐵矽合金，可作為能量轉換的媒介，是馬達、發電機、壓縮機、變壓器…等的核心材料。為消除衝製成形後的應力殘留，ES鐵芯必須進行退火以回復其電磁特性。但不適當的退火易使ES塗膜剝離、劣化鐵芯的層間絕緣，進而降低機電設備之效能。本文針對ES在「氣密爐」中的退火附著性進行研究，發現迥異於非氣密爐的結果：「絕對無水（僅有少量O2）」或「絕對無氧（僅有少量H2O）」之氮氣爐氛均不會劣化退火附著性。但當水氧並存於氮氣爐氛時，O2僅0.025v/v%就有明顯劣化之效果。由微結構分析，各退火片的截面元素分布與變化受退火爐氛與底材合金組成之影響，進而決定了退火附著性。本研究顯示爐氛的效應複雜，其調控是決定退火結果之關鍵。

Electrical steels (ES) are the core for electrical motors, power generators…etc. To restore the electromagnetic property of ES after stamping, stress-relieving annealing is often adopted. However, annealing can be very destructive to the insulation coating on ES. Inappropriate annealing usually results in coating adhesion failure, which severely affects the performance of ES facilities. In the study, effects of furnace atmosphere and substrate (alloying composition) on the post-annealing adhesion capability of ES coating were investigated for ES annealed in the ''air-tight” furnace. Neither ''O2-containing and absolutely dry'' nor ''humidity-containing and absolutely oxygen-free'' nitrogen atmosphere was revealed deteriorative to the adhesion, which opposes to the previous results obtained from the “non-air-tight” furnace. However, when humidity and oxygen coexist, 0.025v/v%O2could lead to an obviously negative effect. Micro-structural analysis (FIB/SEM/EDS/GDS) showed that the cross-sectional distribution of elements is affected by the furnace atmosphere and the alloy composition of ES substrate, which dominates the post-annealing adhesion capability. The furnace atmosphere was revealed to have complex effects on the substrate of annealed ES, and the control of atmosphere is very critical to the annealing result.