Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1983-03-15
1985-12-24
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148 3155, H01F 104
Patent
active
045604231
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing a non-oriented electromagnetic steel sheet having excellent magnetic properties. More specifically, the present invention relates to a process for producing a high-grade non-oriented electromagnetic steel sheet of grade S8 or grade S7 which is more excellent than the non-oriented electromagnetic steel sheet of grade S9 presently prescribed in JIS C 2552 as being the most excellent.
BACKGROUND TECHNIQUE
A non-oriented electromagnetic steel sheet of grade S9, which is presently considered to be of the highest grade, is relatively frequently used as the magnetic core material for large-sized rotary machines and the like. High-grade non-oriented electromagnetic steel sheets exhibit a low watt loss, but the magnetic flux density thereof is poor. For this reason, electric companies do not always use high-grade non-oriented electromagnetic steel sheets as the magnetic core material for large-sized rotary machines but instead use grain-oriented silicon steel sheets which have a high magnetic flux density and are expensive.
Recently, it has been considered whether a high-grade non-oriented electromagnetic steel sheet having qualities such that the sheet can be satisfactorily used as the magnetic core material for large-sized rotary machines, while recently the aim being to conserve energy and reduce the cost of production. Therefore, there has been a great demand for a higher-grade non-oriented electromagnetic steel sheet having a lower watt loss and an improved magnetic flux density as compared with the grade S9 non-oriented electromagnetic steel sheet.
The watt loss of a non-oriented electromagnetic steel sheet can be reduced by increasing the silicon or aluminum content in the sheet and by increasing the size of the crystal grains of the product. However, increasing the silicon or aluminum content and increasing the size of the crystal grains by, for example, enhancing the finishing-annealing temperature of a steel strip cause the resultant product to exhibit a decreased magnetic flux density.
Several proposals have been made for producing a high-grade non-oriented electromagnetic steel sheet of grade S7 or grade S8. For example, Japanese Laid-open Patent Application No. 53-66816 discloses a process for producing a non-oriented electromagnetic steel sheet including a so-called double-stage cold-rolling in which a hot-rolled steel sheet is subjected to cold-rolling twice and to intermediate annealing between the first and second cold-rolling steps. In accordance with this process, the sulfur content and the oxygen content in a silicon steel are restricted to trace levels of 0.005% or less and 0.0025% or less, respectively, so as to suppress the formation of fine inclusions in the steel, thereby not hindering crystal growth during annealing; the sheet is subjected to intermediate annealing at a temperature of from 900.degree. C. to 1050.degree. C. for a relatively long period of, for example, from 2 to 15 minutes so as to form large crystal grains having an average grain diameter of 0.07 mm or more; and, the resultant steel having an intermediate sheet thickness is subjected to cold-rolling and is subjected finally to finishing-annealing at a temperature of from 930.degree. C. to 1050.degree. C. for a sufficient period of from 2 to 15 minutes so that the crystal grains have orientations which are desirable for the magnetic flux density of the sheet, thereby improving the magnetic properties of the final product.
However, since this process requires a relatively long period of time (2 to 15 minutes) for both intermediate annealing and final finishing-annealing, internal oxidation of the steel sheet is likely to occur due to the annealing atmosphere, possibly resulting in deterioration of the magnetic properties of the final product. Since internal oxidation of the steel sheet is likely to occur particularly in the final finishing-annealing step, a long annealing period promotes deterioration of the magnetic properties of the final product.
REFERENCES:
patent: 3203839 (1965-08-01), Takahashi
patent: 3935038 (1976-01-01), Shimoyama et al.
patent: 3948691 (1976-04-01), Matsushita et al.
patent: 4204890 (1980-05-01), Irie et al.
Hiromae Yoshitaka
Miyoshi Kunisuke
Shimoyama Yoshiaki
Nippon Steel Corporation
Sheehan John P.
LandOfFree
Process for producing a non-oriented electromagnetic steel sheet does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing a non-oriented electromagnetic steel sheet, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing a non-oriented electromagnetic steel sheet will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1477570