Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1989-10-12
1991-04-23
Willis, Prince E.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148 3, 148112, H01F 1047
Patent
active
050097261
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of making non-oriented silicon steel sheets having excellent magnetic properties.
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 to obstacles to movements of magnetic domain walls and deteriorate not only the magnetic flux densities under a low magnetic field and the characteristic of 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.
It is known that coarser precipitates are preferable for the movements of the magnetic domain walls during magnetization. Based on such background, there has been disclosed prior art trying to provide the precipitations and coarsenings of AlN or MnS before the recrystallization annealing in the processes of making the electrical steel sheets. For example, Japanese Patent Laid-Open Specification 38814/74 checks re-solution of the coarse AlN during a slab soaking by lowering the heating temperature thereof; Japanese Patent Laid-Open Specification 22,931/81 lowers amounts of S and O accompanying growthes of fine non-metallic inclusions; Japanese Patent Laid-Open Specification 8,409/80 control formation of sulphides by addition of Ca or REM; Same 108,318/77, 41,219/79 and 123,825/83 coasen AlN by brief soaking of the slab before the hot rolling; and Same 76,422/79 utilizes self-annealing effect by coiling at super high temperature after hot rolling for coarsing AlN and accelerating growth of ferrite grain.
From a viewpoint of saving the energy in the process, it is advantageous to carry out a hot direct rolling from the continuous casting of slab when performing the hot rolling. However, if depending upon this process, a problem occurs that the coarse precipitations of AlN and MnS are insufficient, and for solving the problem, the slab is subjected to the brief soaking before the hot rolling.
However, although the soaking time is short, such a process which once transfers the slab into the heating and soaking furnaces, could not enjoy merits of saving energy brought about by the hot direct rolling, and further for providing precipitation of AlN, if the soaking time is short, the precipitation will be non-uniform at the inside and outside of the slab.
DISCLOSURE OF THE INVENTION
In view of these problems of the prior art, in the invention the slab is directly sent to the hot rolling without the brief soaking, whereby others than AlN precipitated during hot rolling check the precipitation of AlN, and a delay time is taken between the roughing and the finish rolling so that precipitating nuclei of AlN are introduced into the steel, and uniform and coarse AlN precipitation is formed by a subsequent annealing treatment, thereby to enable to provide uniform and satisfied ferrite grain growth at the recrystallization annealing.
That is, the invention comprises roughing a slab immediately after continuously casting thereof to thickness of more than 20 mm at reduction rate of more than 10% without the brief soaking at a specified temperature range, 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 inavoidable impurities; having a time interval of more than 40 sec at temperature range where the surface temperature of the roughed bar is more than 900.degree. C. till a following finish rolling; performing a finish rolling and coiling at temperature of not more than 650.degree. C.; annealing the hot rolled band by soaking it at the temperature of 800.degree. to 950.degree. C. for a period of time satisfying intermediate annealing and a final continuous annealing at range of temperature between 850.degree. and 1100.de
REFERENCES:
patent: 4066479 (1978-01-01), Shimoyama et al.
patent: 4204890 (1980-05-01), Irie et al.
Hosoya Yoshihiro
Jitsukawa Masaharu
Nishimoto Akihiko
Tomita Kunikazu
Urabe Toshiaki
Flatter R. D.
Nields Henry C.
NKK Corporation
Willis Prince E.
LandOfFree
Method of making non-oriented silicon steel sheets having excell 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 silicon steel sheets having excell, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of making non-oriented silicon steel sheets having excell will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1619273