U.S. patent application number 13/880278 was filed with the patent office on 2013-11-07 for annualing separation agent for producing grain-oriented silicon steel with smooth surface and good magnetic property.
The applicant listed for this patent is Yaming Ji, Dengfeng Li, Guobao Li, Yunpeng Xu, Yongjie Yang, Zipeng Zhao. Invention is credited to Yaming Ji, Dengfeng Li, Guobao Li, Yunpeng Xu, Yongjie Yang, Zipeng Zhao.
Application Number | 20130292005 13/880278 |
Document ID | / |
Family ID | 45993115 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130292005 |
Kind Code |
A1 |
Zhao; Zipeng ; et
al. |
November 7, 2013 |
ANNUALING SEPARATION AGENT FOR PRODUCING GRAIN-ORIENTED SILICON
STEEL WITH SMOOTH SURFACE AND GOOD MAGNETIC PROPERTY
Abstract
An annealing separator for manufacturing grain-oriented silicon
steel with mirror-like surface having good magnetic performance
consists of the composition of which is 77.about.98 by wt % of
Al.sub.2O.sub.3 powder, 1.about.8 by wt % of alkaline earth powder,
1.about.15 by wt % of alkali metal chloride and/or alkaline earth
metal chloride. The annealing separator of the invention can avoid
forming a glass-film undercoating on the surface of the steel sheet
during high-temperature annealing, and at the same time, the oxide
embedded at near-surface of the sheet is removed by means of
corrosive reaction of the chloride, so that a produce with smooth
surface and stable magnetic performance is obtained.
Inventors: |
Zhao; Zipeng; (Shanghai,
CN) ; Ji; Yaming; (Shanghai, CN) ; Yang;
Yongjie; (Shanghai, CN) ; Li; Guobao;
(Shanghai, CN) ; Li; Dengfeng; (Shanghai, CN)
; Xu; Yunpeng; (Shanghai, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zhao; Zipeng
Ji; Yaming
Yang; Yongjie
Li; Guobao
Li; Dengfeng
Xu; Yunpeng |
Shanghai
Shanghai
Shanghai
Shanghai
Shanghai
Shanghai |
|
CN
CN
CN
CN
CN
CN |
|
|
Family ID: |
45993115 |
Appl. No.: |
13/880278 |
Filed: |
April 14, 2011 |
PCT Filed: |
April 14, 2011 |
PCT NO: |
PCT/CN2011/072771 |
371 Date: |
July 18, 2013 |
Current U.S.
Class: |
148/22 |
Current CPC
Class: |
C22C 38/02 20130101;
C21D 1/68 20130101; C21D 1/70 20130101; C21D 1/26 20130101; C22C
38/06 20130101; C22C 38/16 20130101; C21D 8/12 20130101; C21D 9/46
20130101; H01F 1/16 20130101; C21D 3/04 20130101; C22C 38/04
20130101 |
Class at
Publication: |
148/22 |
International
Class: |
C21D 1/70 20060101
C21D001/70 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 25, 2010 |
CN |
201010518037.5 |
Claims
1. An annealing separator for manufacturing a grain-oriented
silicon steel with good magnetic performance, which consists of a
composition as follows: 77.about.98% by weight of Al.sub.2O.sub.3
powder; 1.about.8% by weight of alkaline earth metal oxide powder;
1.about.15% by weight of alkali metal chloride and/or alkaline
earth metal chloride.
2. The annealing separator for manufacturing a grain-oriented
silicon steel with good magnetic performance according to claim 1,
wherein the alkaline earth metal oxide comprises BeO, MgO, CaO, SrO
or BaO.
3. The annealing separator for manufacturing a grain-oriented
silicon steel with good magnetic performance according to claim 1,
wherein the alkali metal chloride comprises LiCl, NaCl, KCl or
RbCl.
4. The annealing separator for manufacturing a grain-oriented
silicon steel with good magnetic performance according to claim 1,
wherein the alkaline earth metal chloride comprises BeCl.sub.2,
MgCl.sub.2, CaCl.sub.2, SrCl.sub.2, BaCl.sub.2 or ZnCl.sub.2.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for manufacturing
grain-oriented silicon steels, especially to an annealing separator
for manufacturing grain-oriented silicon steels with mirror-like
surface having excellent magnetic performance.
DESCRIPTION OF THE PRIOR ART
[0002] Grain-oriented silicon steel shall be subjected to
decarburization annealing protected in a H.sub.2--N.sub.2
atmosphere, after being subjected to processes of hot-rolling,
normalizing and cold rolling, and accordingly the rolling stress is
relieved and preliminary recrystallization is formed, and
meanwhile, wet gas is introduced into a furnace for controlling a
carbon content in the steel belt below 30 ppm to prevent the final
product from magnetic aging. The steel belt will be oxidized when
subjected to the decarburization annealing to form an oxide layer
mainly consisting of SiO.sub.2 and Fe.sub.2SiO.sub.4, which will
negatively affect the following decarburization. In the following
high-temperature annealing process, the oxide layer undergoes
chemical reaction with the annealing separator coated on surfaces
of the steel belt, and produces a glass-film undercoating mainly
consisting of Mg.sub.2SiO.sub.4. The glass-film undercoating has
the function of preventing the steel belt from bonding and
purifying the steel during the high-temperature annealing.
[0003] The Mg.sub.2SiO.sub.4 glass-film undercoating on the surface
of the grain-oriented silicon steel has relative high hardness,
which results in a relative poor punching performance of the steel
sheet, which is generally thousands of times; and, an embedded
combination between the glass-film undercoating and a body of the
steel sheet hinders magnetic domain wall movement, and increases
magnetic hysteresis loss.
[0004] In order to improve the punching performance of the
grain-oriented silicon steel and further improve the magnetic
performance, Japanese develop a grain-oriented silicon steel
without the glass-film undercoating. Japanese patent JP49096920
discloses a method that removes glass-film undercoating on the
surface of the grain-oriented silicon steel by means of acid
pickling. However, in order to completely wash out the glass-film
undercoating with a thickness of 10 .mu.m (including the oxide
embedded into the steel sheet), the steel shall be immersed in
strong acid for a long period, which results in the problems of
high cost, environmental pollution of the agent and the like.
[0005] Japanese patent JP05156362A discloses that Al.sub.2O.sub.3
is applied as a high-temperature annealing separator.
Al.sub.2O.sub.3 does not react with the oxide layer or the body of
steel sheet, so that the grain-oriented silicon steel without the
glass film undercoating can be obtained directly. However, the
method cannot remove the oxide layer or embedded oxide formed
during decarburizing annealing, which is disadvantage in term of
improving the magnetic performance.
[0006] To solve this problem, Japanese patent JP2003247024 relates
to a method in which the ratio of PH.sub.2O/PH.sub.2 is controlled
to form an atmosphere having a low degree of oxidizability, thus no
Fe based oxide is formed, a separator mainly of Al.sub.2O.sub.3
then is coated to obtain grain-oriented steel with smooth surface.
However, if the degree of oxidizablility is too low during
decarburizing, it will result in the difficulty of decarburization.
In Japanese patent JP05156364A, after the decarburization annealing
is completed, an oxide layer on the surface of the steel sheet is
removed by means of acid pickling, and then a separator mainly of
Al.sub.2O.sub.3 is coated.
[0007] In U.S. Pat. No. 554,719, MgO+SiO.sub.2 is used as an
annealing separator, which forms loose magnesium silicate on
surfaces of a steel sheet during a secondary recrystallization
annealing step, then the loose magnesium silicate is removed by
brushing and washing, so that a product without glass-film
undercoating is obtained.
[0008] In Japanese patent JP2000038615, magnesia and alumina added
with chloride are used as an annealing separator, the formed glass
film undercoating is removed by means of interfacial reaction of
(2/3)MCl.sub.3+Fe+(3/2)O.sub.2.fwdarw.M.sub.2O.sub.3+FeCl.sub.2.uparw.,
so that a product without any glass-film undercoating is
obtained.
[0009] JFE, a Japanese company, uses Al.sub.2O.sub.3 and the like,
which does not react with the surface of the steel sheet, as a
high-temperature annealing separator to directly obtain a
grain-oriented silicon steel without any glass-film undercoating.
In such a method, in order to completely eliminate near-surface
oxide impurity of the steel sheet, the dew point for decarburizing
shall be so strictly controlled that no Fe based oxide is formed on
the surface of the steel sheet. However, this will inevitably cause
the problem of decarburization and nitridation.
[0010] Armco company (now AK company), a US company, uses magnesia,
which is added with SiO.sub.2, as an annealing separator, wherein
the loose magnesium silicate formed on the steel sheet during a
secondary recrystallization annealing step will benefit in
introducing annealing protection gas into interlayer portion of the
steel sheet for purifying the steel. However, generally, such a
method cannot completely wash out the magnesium silicate on the
surface, and cannot completely remove the embedded oxide at the
near surface of the iron sheet, either, which restricts the effect
of lowering iron core loss.
[0011] NSC, which is a Japanese company, uses magnesia, which is
added with chloride, as an annealing separator. However, adding
large amount of chloride will result in certain corrosion to the
surface of the steel sheet during a secondary recrystallization
annealing, which will affect surface inhibitor, the secondary
recrystallization will be unstable.
TABLE-US-00001 TABLE 1 Main composition of the separator
fundamental U.S. Pat. 100% by weight of No undercoating reaction
No. 3,785,882 Gross Al.sub.2O.sub.3 occurs US554719 (35-85% by
weight)MgO + Loose undercoating, which (15-65% by weight) SiO.sub.2
can be easily removed, is formed on the steel sheet surface
JP08269560 MgO + Cl The undercoating is re- A An amount of Cl added
is moved by interfacial reac- controlled at 0.05-0.5% by tion of
(CaC1.sub.2 + Fe weight (1/2)O.sub.2 .fwdarw.CaO +
FeC1.sub.2.uparw.)
SUMMARY OF THE INVENTION
[0012] The object of the present invention is to provide an
annealing separator for manufacturing grain-oriented silicon steel
with mirror-like surface having good magnetic performance, which
can prevent the glass-film undercoating from forming on the steel
sheet, meanwhile the embedded oxide at the near-surface of sheet
can be removed by means of corrosion reaction with the chloride, so
that a product with smooth surface and stable magnetic performance
can be obtained.
[0013] In order to obtain the above-described object, the technical
solution of the present invention is that:
[0014] An annealing separator for manufacturing grain-oriented
silicon steel with mirror-like surface having good magnetic
performance consists of a composition as follows: 77.about.98% by
weight of Al.sub.2O.sub.3 powder, 1.about.8% by weight of alkaline
earth metal oxide powder, 1.about.15% by weight of alkali metal
chloride and/or alkaline earth metal chloride.
[0015] Further, the alkaline earth metal oxide comprises BeO, MgO,
CaO, SrO, or BaO.
[0016] In addition, the alkali metal chloride comprises LiCl, NaCl,
KCl, or RbCl.
[0017] alkaline earth metal chloride comprises BeCl.sub.2,
MgCl.sub.2, CaCl.sub.2, SrCl.sub.2, BaCl.sub.2 or ZnCl.sub.2.
[0018] It is found by experiment that it will be effective for
removing the oxide layer at the near-surface of sheet by applying a
substance that does not react with the oxide layer of the sheet as
the annealing separator during high-temperature annealing, the
substance is added with a few amount of alkaline earth metal oxide
for introducing moisture not higher than 2.5 wt %, and a certain
amount of chloride is also added, so that the moisture reacts with
the chloride ion contained in the chloride additive to form
corrosive solution with acidity, which is good advantageous for
removing oxide layer at the near-surface of sheet.
[0019] By adding and stirring water, the annealing separator for
the grain-oriented silicon steel with mirror-like surface of the
invention forms a coating liquid having a certain concentration,
then coating on the surface of the decarburized sheet is carried
out. After the completion of coating, the product is baked under a
temperature not higher than 300.degree. C. for more than 30 s, so
as to expel free moisture in the separator. At this time, the
separator forms a substance having micropores, and the main
composition of the substance is a mixture of Al.sub.2O.sub.3,
Ca(OH).sub.2 and one or more kinds of chloride, which has good
permeability. The primary chemical reaction during the hydrolysis
is
CaO+H.sub.2O.dbd.Ca(OH).sub.2 {circle around (1)}
[0020] In a preliminary phase of the high-temperature annealing,
Ca(OH).sub.2 is subjected to a decomposition reaction and again
produces CaO and releases moisture when the temperature is higher
than 580.degree. C. The presence of the moisture at one hand
provides some solution, and at the other hand reacts with the
chlorine ion to form an acid substance of HCl, which has a certain
corrosion function. Chemical reactions occurred in subsequence
during the high annealing are as follows:
Ca(OH).sub.2.dbd.CaO+H.sub.2O {circle around (2)}
H.sub.2O+Cl.sup.-HCl.uparw.+OH.sup.-{circle around (3)}
[0021] HCl in gas phase penetrates through the separator, reacts
with the oxide layer of the sheet, and promote the reaction
designated by the chemical equilibrium {circle around (3)}
rightward, so that the reaction occurs continuously. The reaction
between HCl and oxide layer is as follows:
2HCl+FeO.dbd.FeCl.sub.2+H.sub.2O.uparw.{circle around (4)}
4HCl+Fe.sub.2SiO.sub.4.dbd.2FeCl+SiO.sub.2+2H.sub.2O.uparw.{circle
around (5)}
[0022] The oxide layer corrupted by HCl degrades to a loose and
porous substance, the binding force of which with the sheet is
reduced substantially. By slightly being pickled and brushed after
high-temperature annealing, such oxide layer can be easily removed.
Thus, the grain-oriented silicon steel with mirror-like surface and
smooth surface can be finally obtained after hot stretching and
flattening process.
[0023] The glass film undercoating formed during the conventional
high-temperature annealing for grain-oriented silicon steel
presents a relative high hardness, which will degrade the punching
performance of the silicon steel sheet, molds will be damaged in
some extents during the manufacturing. Meanwhile, a pinned
structure of the oxide in the body of sheet hinders the magnetic
domain wall movement, which will negatively affect the magnetic
performance. The grain-oriented silicon steel without undercoating
can substantially improves the processability of the silicon steel,
and the processability thereof can be further improved due to the
absence of the pinned structure, so that a product with extra low
iron core loss can be obtained.
[0024] Prior to the present invention, patents for obtaining
grain-oriented surface silicon steel mainly relate to MgO and
chloride or Al.sub.2O.sub.3. The former will result in instability
of the magnetic performance, and the latter cannot remove the
embedded oxide formed during decarburizing annealing process. Some
one utilizes the Al.sub.2O.sub.3 separator added with chloride,
however, the chloride itself needs the assistance of certain
moisture for reacting with the embedded oxide to remove the
same.
[0025] The invention inventively introduces the alkaline earth
metal oxide, based on the water solubility of the alkaline earth
metal oxide, the moisture introduced during the high-temperature
annealing can be controlled easily. Such a method is easy, and can
stably obtain excellent grain-oriented silicon steel products. The
apparatus concerned is conventional apparatus for producing
grain-oriented steel, which has excellent practicability and
spreadability, which features good expectation of popularizing.
BRIEF DESCRIPTION OF DRAWINGS
[0026] FIG. 1 is a sectional optical photograph of a steel sheet of
comparative example 1 (separator: MgO 65Wt % plus SiO.sub.2 35 Wt
%).
[0027] FIG. 2 is a sectional optical photograph of a steel sheet of
comparative example 2 (separator: MgO 90Wt % plus CaCl.sub.2 Wt
%).
[0028] FIG. 3 is a sectional optical photograph of a steel sheet of
comparative example 3 (separator: Al.sub.2O.sub.3 100 Wt %).
[0029] FIG. 4 is a sectional optical photograph of a steel sheet of
an embodiment of the invention (the separator: Al.sub.2O.sub.3 86
Wt % plus CaO 4 Wt % plus MgCl.sub.2 10 Wt %).
DETAILED DESCRIPTION OF THE INVENTION
[0030] Hereinafter, the present invention will be described in
connection with embodiments.
[0031] A 500 Kg-vacuum furnace is used for steel-smelting, the
chemical composition of a steel blank is (in Wt %): 0.045% by
weight of C, 3.25% by weight of Si, 0.006% by weight of S, 0.027%
by weight of Als, 0.006% by weight of N, 0.15% by weight of Cu,
0.012% by weight of Mn and a balance consisting of Fe and
inevitable impurities. After being heated under 1150.degree. C.,
the blank is hot rolled to form a hot rolled sheet with a thickness
of 2.6 mm. The hot rolled sheet is normalized and annealed for 1
minutes, and then is pickled and cold rolled to form the sheet with
a final thickness of 0.285 mm. The cold rolled sheet undergoes
decarburizing annealing treatment under 835.degree. C. for 120 s,
so there are two levels of the oxygen content on the surface: 0.8
and 1.6 g/m.sup.2; after the process of nitriding, the nitrogen
content of the steel sheet is 250 ppm. The decarburized and
annealed sheet is coated by the annealing separator (the material
proportion is shown in Table 2), after being wound, the sheet
undergoes high-temperature annealing at 1200.degree. C., which
temperature is held for 20 hours, in the protective atmosphere of
dry nitrogen and hydrogen, then the sheet is coated with an
insulation coating, stretched and flattened, and annealed after
unwound.
TABLE-US-00002 TABLE 2 (% by weight) alkali metal alkaline earth
chloride/alkaline description Al.sub.2O.sub.3 metal oxide earth
chloride Embodiment 1 98 CaO 1 MgCl.sub.2 1 Embodiment 2 86 CaO 4
MgCl.sub.2 10 Embodiment 3 77 CaO 8 MgCl.sub.2 15 Embodiment 4 86
BeO 4 LiCl 10 Embodiment 5 86 MgO 4 NaCl 10 Embodiment 6 86 SrO 4
KCl 10 Embodiment 7 86 BaO 4 RbCl 10 Embodiment 8 86 MgO 4 BeCl2 10
Embodiment 9 86 SrO 4 CaCl2 10 Embodiment 10 86 BaO 4 SrCl2 10
Embodiment 11 86 CaO 4 BaCl2 10 Embodiment 12 86 CaO 4 ZnCl2 10
comparative 65 parts of MgO + 35 parts of SiO.sub.2 example 1
comparative 90 parts of MgO + 10 parts of CaCl.sub.2 example 2
comparative Al.sub.2O.sub.3 100 parts example 3
[0032] The average values of the electromagnetic performance of the
resulted products and the surface qualities thereof are shown in
table 3.
TABLE-US-00003 TABLE 3 Electromagnetic Surface performance oxygen
P.sub.17/50, Separator content B.sub.8, T W/kg Surface appearance
Embodiment 1 0.8 g/m.sup.2 1.897 0.753 Smooth surface, no
undercoating 1.6 g/m.sup.2 1.905 0.745 Smooth surface, no
undercoating Embodiment 2 0.8 g/m.sup.2 1.891 0.783 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.897 0.774 Smooth surface, no
undercoating Embodiment 3 0.8 g/m.sup.2 1.899 0.735 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.903 0.734 Smooth surface, no
undercoating Embodiment 4 0.8 g/m.sup.2 1.888 0.779 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.897 0.748 Smooth surface, no
undercoating Embodiment 5 0.8 g/m.sup.2 1.889 0.776 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.895 0.773 Smooth surface, no
undercoating Embodiment 6 0.8 g/m.sup.2 1.900 0.769 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.900 0.743 Smooth surface, no
undercoating Embodiment 7 0.8 g/m.sup.2 1.890 0.782 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.903 0.775 Smooth surface, no
undercoating Embodiment 8 0.8 g/m.sup.2 1.895 0.768 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.893 0.760 Smooth surface, no
undercoating Embodiment 9 0.8 g/m.sup.2 1.899 0.772 Smooth surface,
no undercoating 1.6 g/m.sup.2 1.903 0.769 Smooth surface, no
undercoating Embodiment 10 0.8 g/m.sup.2 1.887 0.766 Smooth
surface, no undercoating 1.6 g/m.sup.2 1.890 0.760 Smooth surface,
no undercoating Embodiment 11 0.8 g/m.sup.2 1.897 0.771 Smooth
surface, no undercoating 1.6 g/m.sup.2 1.910 0.743 Smooth surface,
no undercoating Embodiment 12 0.8 g/m.sup.2 1.887 0.775 Smooth
surface, no undercoating 1.6 g/m.sup.2 1.899 0.762 Smooth surface,
no undercoating comparative 0.8 g/m.sup.2 1.927 0.705 The surface
includes example 1 partial undercoating 1.6 g/m.sup.2 1.921 0.720
The surface includes complete undercoating comparative 0.8
g/m.sup.2 1.825 0.997 The surface includes example 2 partial
undercoating 1.6 g/m.sup.2 1.857 0.897 The surface includes partial
undercoating comparative 0.8 g/m.sup.2 1.865 0.903 The surface
includes example 3 partial undercoating 1.6 g/m.sup.2 1.847 0.937
The surface includes partial undercoating
[0033] It can be seen from FIGS. 1-4 and Table 3 that there is few
oxide residual existing on the surface of the silicon steel sheet
coated with the separator of the invention, and the magnetic
performance of the steel sheet are good. Thus, it can be seen that
the grain-oriented steel sheet with mirror-like surface having good
magnetic performance can be manufactured by the effective finish
process on the surface of the grain-oriented silicon steel in the
present invention.
[0034] On one hand, the high-temperature annealing separator of the
present invention effectively purifies the steel and prevents coils
of the steel from binding, and on the other hand, the present
invention provides a corrosive atmosphere during the annealing with
high temperature to remove the oxide layer at near-surface, so that
grain-oriented silicon steel with mirror-like surface having good
magnetic performance can be produced.
* * * * *