Forsterite insulating films formed on surface of a grain-oriented silicon steel sheet having a high magnetic induction and a method of forming the same
US4127429A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 27, 1977 |
| Grant date | Nov 28, 1978 |
| Priority date | — |
| Expiry date | Jun 27, 1997 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D8/1283
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A forsterite insulating film having a good adhesion property to a grain-oriented silicon steel sheet with a high magnetic induction is composed of forsterite grains having a mean grain size of not more than 0.7 .mu.m. The forsterite insulating film is formed by annealing a coil of a cold rolled silicon steel strip having a final gauge in an annealing furnace under an inert gas atmosphere at a constant temperature keeping stage of 800.degree.-920.degree. C so as to fully develop secondary recrystallized grains and then under hydrogen gas atmosphere at a temperature rising stage up to 1,150.degree.-1,250.degree. C and a constant temperature keeping stage of 1,150.degree.-1,250.degree. C during the final annealing, provided that an average dew point of the atmosphere is within a range of -20.degree. C to +20.degree. C in the temperature rising stage up to 1,150.degree.-1,250.degree. C and not more than +10.degree. C in the constant temperature keeping stage of 1,150.degree.-1,250.degree. C.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.