Metal treatment – Process of modifying or maintaining internal physical... – Magnetic materials
Patent
1989-10-17
1992-12-08
Sheehan, John P.
Metal treatment
Process of modifying or maintaining internal physical...
Magnetic materials
148112, H01F 104
Patent
active
051694573
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of making non-oriented electrical steel sheets.
BACKGROUND OF THE INVENTION
Important factors in governing magnetic properties of electrical steel sheets include sizes and dispersing conditions of Aln and MnS precipitates in steels. These precipitates are obstacles to movements of magnetic domain walls and deteriorate not only the magnetic flux density under a low magnetic field but also the iron loss. In addition, they hinder gain growth during recrystallization annealing, and immature gain growth of ferrite grains negatively influence developments of recrystallization texture preferable to the magnetic properties.
It is known that rougher and coarser precipitates are preferable for the movements of the magnetic domain walls during magnetization. Based on such background, there has been disclosed in the prior art attempts to provide coarser precipitates 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 disolution of the coarse AlN during slab soaking by lowering the heating temperature thereof; Japanese Patent Laid-Open Specification 22,931/81 lowers the amounts of S and O accompanying growthes of fine non-metallic inclusions; Japanese Patent Laid-Open Specification 8,409/80 controls formation of sulphides by addition of Ca or REM; Japanese Patent Laid-Open Specifications 108,318/77, 41,219/79 and 123,825/83 coarsen AlN by brief soaking of the slab before the hot rolling; and Japanese Patent Laid-Open Specification 76,422/79 utilizes a self-annealing effect by coiling at super high temperature after hot rolling for coarsening AlN and accelerating growth of ferrite grain.
From a viewpoint of saving energy in the process, it is advantageous to carry out a hot direct rolling from the continuous casting of a slab when performing the hot rolling. However, if this process is used, a problem occurs that the coarse precipitations of AlN and MnS are made insufficient. To solve this 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 the merits of saving energy brought about by the hot direct rolling. Furthermore, 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 Al and N are maintained in solution with respect to species other than AlN inevitably precipitated during hot rolling, and uniform and coarse AlN precipitation is formed by a subsequent annealing treatment. Uniform and satisfactory ferrite grain growth at the recrystallization annealing is thereby provided.
That is, the invention comprises hot rolling a slab immediately after continuously casting thereof without 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 %; coiling at a temperature of not more than 650.degree. C.; annealing the hot rolled plate by soaking it at the temperature of 800.degree. to 1000.degree. C. for a period of time satisfying more than one cold rollings having interposed therebetween intermediate annealings; and a final continuous annealing at a temperature range between 850.degree. and 1100.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows, with respect to 3% Si steel, influences of the soaking time of the hot rolled band on the average size of AlN during hot rolling and on the magnetic properties; and
FIG. 2 shows optimum ranges of the soaking temperature and the soaking time during annealing of the hot band.
DETAILED DESCRIPTION OF THE INVENTION
In th
Hosoya Yoshihiro
Jitsukawa Masaharu
Nishimoto Akihiko
Tomita Kunikazu
Urabe Toshiaki
NKK Corporation
Sheehan John P.
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-958538