Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1990-04-06
1991-12-24
Dean, R.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148 2, C21D 812
Patent
active
050749307
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of making non-oriented electrical steel sheets.
BACKGROUND OF THE INVENTION
As important factors of governing magnetic properties of electrical steel sheets, sizes and dispersing conditions of AlN and MnS precipitates in steels are taken up. This is why these precipitates themselves become obstacles to movements of magnetic domain walls and deteriorate not only the magnetic flux densities under a low magnetic field but also the iron loss, and in addition they hinder grain growth during recrystallization annealing, and immature grain growth thereby of ferrite grains give bad influences to developments of recrystallization texture preferable to the magnetic properties.
Coarser precipitates are preferable for grain boundary migration and magnetic domain walls during magnetization. It is important to provide the precipitations and coarsenings of AlN or MnS before the recrystallization annealing in the processes of making the electrical steel sheets.
For saving energy, it is desirable to make use of the sensible heat of the continuous cast slab by avoiding the slab temperature from going down and carrying out a hot rolling after a brief heating of the high temperature slab. However, since such a process takes an extremely short time for the slab cooling and heating in comparison with a process of reheating a cold slab as ordinarily done, a coarse precipitation of AlN taking place is not prospective.
Therefore, it has been proposed, for example, in Japanese Patent Laid-Open Nos. 108,318/77 and 41,219/79 to carry out a brief soaking before hot rolling the slab so as to coarsen the precipitation of AlN therebetween as said, and then reheat the slab to reduce a milling load of the hot rolling and to uniformalize the slab temperature for avoiding deterioration of the shape of the hot rolled sheet.
However, there arise problems, since the conventional processes require the soaking about 1000.degree. C. for more than 40 min to coarse precipitation of AlN, surface properties are deteriorated by occurrences of scales in such a period, a cover should be needed for the soaking, so that an operating efficiency is lowered by attaching and removing the cover. Further, this process could not avoid non-uniformity of the temperature due to positioning of the slab, and accordingly the magnetic properties become non-uniform by non-uniformity in coarsening of AlN precipitates.
DISCLOSURE OF THE INVENTION
The present invention has been realized in view of such circumstances, where the energy is saved by brief heating the slab while it has the high temperature for usefully utilizing the sensible heat of the slab, a heat cycle of the slab is optimized, thereby enabling to coarsen the AlN precipitates in a period of short time, which has not been expected in the prior art.
That is, the invention comprises cooling down a slab after continuous casting between 700.degree. and 900.degree. C., heating it in a heating furnace for more than 5 min between 1000.degree. and 1100.degree. C., hot rolling and coiling a steel band lower than 650.degree. C., said slab containing C: not more than 0.005 wt %, Si: 1.0 to 4.0 wt %, Mn: 0.1 to 1.0 wt %, P: not more than 0.1 wt %, S: not more than 0.005 wt %, Al: 0.1 to 2.0 wt %, balance being Fe and unavoidable impurities; annealing it, after pickling, at temperature of 800.degree. to 1000.degree. C. for a period of time satisfying intermediate annealing and final continuous annealing at range of temperature between 850.degree. and 1100.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows influences of cooling temperature of a slab after casting and heating temperature of the slab on magnetic properties of a product.
DETAILED DESCRIPTION OF THE INVENTION
In the invention, the operation is performed with the cooling after continuous casting between 700.degree. and 900.degree. C., the heating in the heating furnace for more than 5 min between 1000.degree. and 1100.degree. C., and the hot rolling on the slab containing C: not more than 0.0
REFERENCES:
patent: 4661174 (1987-04-01), Miyoshi et al.
patent: 4666534 (1987-05-01), Miyoshi et al.
patent: 5009726 (1991-04-01), Nishimoto et al.
Hosoya Yoshihiro
Jitsukawa Masaharu
Nishimoto Akihiko
Tomita Kunikazu
Urabe Toshiaki
Dean R.
NKK Corporation
Wyszomierski George
LandOfFree
Method of making non-oriented electrical steel sheets does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of making non-oriented electrical steel sheets, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of making non-oriented electrical steel sheets will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-41198