METHODE DE FABRICATION D'ACIER AU SILICIUM A FORTE PERMEABILITE

PROCESSING FOR HIGH PERMEABILITY SILICON STEEL

Abrégé anglais

PROCESSING FOR HIGH PERMEABILITY SILICON STEEL
ABSTRACT OF THE DISCLOSURE
A process for producing silicon steel having a cube-on-edge
orientation and a permeability of at least 1850 (G/Oe) at 10 oersteds, which
includes the steps of: preparing a melt of steel consisting essentially of,
by weight, up to 0.07% carbon, from 2.6 to 4.0% silicon, from 0.03 to 0.24%
manganese, from 0.01 to 0.097% of material from the group consisting of
sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.02% nitrogen,
up to 0.5% copper, up to 0.0035% boron, balance iron; casting the steel,
hot rolling the steel, cold rolling the steel, decarburizing the steel, coating
the steel with a base coating containing a nitrogen-bearing compound from
the group consisting of (NH4)2SO4, Fe(NO3)3, Al(NO3)3,Mg(NO3)2 and
Zn(NO3)2, and final texture annealing the steel.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. In a process for producing electromagnetic silicon
steel having a cube-on-edge orientation and a permeability of
at least 1850 (G/O) at 10 oersteds, which process includes the
steps of:
preparing a melt of silicon steel consisting essen-
tially of, by weight, up to 0.07% carbon, from 2.6 to 4.0%
silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.09% of
material from the group consisting of sulfur and selenium, from
0.015 to 0.04% aluminum, up to 0.02% nitrogen, up to 0.5% copper,
up to 0.0035% boron, balance iron;
casting said steel;
hot rolling said steel into a hot rolled band;
cold rolling said steel at a reduction of at least 80%;
decarburizing said steel; and
final texture annealing said steel;
the improvement comprising the steps of coating the
surface of said steel with a base coating consisting essentially
of:
(a) 100 parts, by weight, of at least one substance
from the group consisting of boron, boron compounds,
sulfur, sulfur compounds, selenium, selenium compounds,
and oxides and hydroxides of magnesium, calcium, aluminum,
titanium and manganese; and
(b) 0.5 to 50 parts, by weight, of at least one
nitrogen-bearing compound from the group consisting of
(NH4)2SO4, Fe(NO3)3, AL(NO3)3, Mg(NO3)2 and Zn(NO3)2;
and final texture annealing said steel;
said steel's texture and magnetic properties being, in
part, attributable to said nitrogen-bearing compound.

2. A process according to claim 1, wherein said
coating has from 1.5 to 5 parts, by weight, of at least one
nitrogen-bearing compound.
3. A process according to claim 1, wherein said
coating contains (NH4)2SO4.
4. A process according to claim 1, wherein said
coating consists essentially of: 100 parts, by weight, of
boron, boron compounds, and oxides and hydroxides of magnesium,
titanium and manganese.
5. A process according to claim 4, wherein said
coating has from 1.5 to 5 parts, by weight, of at least one
nitrogen-bearing compound.
6. A process according to claim 4, wherein said
coating contains (NH4)2SO4.
7. A process according to claim 1, wherein said
coating consists essentially of: 100 parts, by weight, of
boron, boron compounds, and oxides and hydroxides of magnesium.
8. A process according to claim 7, wherein said
coating has from 1.5 to 5 parts, by weight, of at least one
nitrogen-bearing compound.
9. A process according to claim 7, wherein said
coating contains (NH4)2S04.

Description

The present in~rention relates to a process util-zic~ a base co2,iag
containing a nitrogen-bearing compound, from the aroup consisting of
~NH4)2SO4~ ~e(N3)3- Al(NO3)3~ Mg~NO3)z alld Zn(1~03~2, i~ t~e manufacturs
of electromagnetic silicon steel having a cube-on-edge orientatlon and a
permeability of at least 1850 (G/Oe) at 10 oersteds.
2û The use of nitrogen in final anneali~g atmospheres has in ma~y
instances improved texture development for the new breed of alumillurr,-
bearina hiah permeability silicon steels, such as those disclosed in U~ited
States Patent No. 3, 85;, 020, which issued on December 17, 1~74. Such ase
has not, howP~rer, beea without problems. Ia annealiag coils of the s~eel,
2S difficulty in di fusing nitrogen through the laps of the coils has been
encountered.
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The present invention provides nitrogen in the annealing enviro~-
ment atld simultaneously overcomes the heretofore referred to difficulties
encountered with nitrogen-bearing annealing atmospheres. It calls for the
use of base coating containing a nitrogen-bearing compound from the group
g (N~4)2S4' Fe(N03)3~ Al(NO3)3~ Mg(NO3) and Z;n(NO )
The nitrogen in the coating has been found to serve the same purpose as
does the ~itrogen in the annealing atmosphere. In the manufacture of grain
oriented silicon steels, base coatings are applied to the steel ~ust prior to
final texture annealing.
.
It is accordingly an object of the present invention to provide a process
utilizing a base coating containing a nitrogen-bearing compound from the
4)2S04. Fe(N03)3, Al(~Jo3)3, Mg(No ) and Z (N
in the manufacture of electromagnetic silicon steel having a cube-on-edge
orientation and a permeability of at least 1850 (G/O ) at 10 oersteds.
.
lS In accordance with the present invention, a melt of silicon steel is
subjected to the conventional steps of casting, hot rolling, cold rolling at a
reduction of at least 80%, decarburizing and final texture annealing; and to
the improvement of adding a nitrogen-bearing compound fromthe group
con9isting of (~H4)2S04, Fe(N03)3, Al(NO3)3, Mg(NO3)2 and Zn(N03)2 to
20 the base coating. Specific processing is not critical and can be in acco~d-
allce with that specified in any number of publications including United
.
States Patent Nos. 3, 855, 018, 3,855, 019, 3, 855,020 and 3, 855, 021. The
melt consists essentially of, by weight up to û. 07% carbon, from 2~ 6 to
4. 0% silic ~n, from 0. 03 to 0. 24% manganese, from Q~ 01 to 0. 09% of
25 material from the group consisting of `sulfur and selenium, from 0. 015 to
:, . .
O. 04% aluminum, up to 0. 02% nitrogen, up to 0. 5% copper, up to 0. 0035~o
boron, balance iron.
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1 The base coating consists essentially of:
(a) 100 parts, by weight, of at least one
substance ~rom the group consisting of boron,
boron compounds, sulfur, sulfur compounds,
selenium, selenium compounds, and oxides and
hydroxides of magnesium, calcium, aluminum,
titanium and manganese; and
(b) 0.5 to 50 parts, by weigh-t of at least
one nitrogen-bearing compound from the group
consisting of ~N~4)2SO4, Fe~NO3)3, AltNO3)3,
Mg(NO3)2 and Zn(NO3)2
The nitrogen-bearing compounds are preferably present in an
amount of from 1.5 to 5 parts, by weight. (NH4)2SO4 is the
preferred nitrogen-bearing compound. A base coating containing
from 1.5 to 5 parts, by weight of (NH4)2S04 and 100 parts~ by
weight, of boron, boron compounds, and oxides and hydroxides
of magnesium is presently preferred. Examples of this coating
appear hereinbelow. Another desirable coating, is believed to
be one containing from 1.5 to 5 parts, by weight of (NH4)2SO4
and 100 parts, by weight, of boron, boron compounds and oxides
and hydroxides of magnesium, titanium and manganese. Such a
coating could contain 100 parts MgO, 10 parts Tio2, 4 parts
MnO2, 1 part H3BO3 and 2 parts (NH4~2SO4.
The following examples are illustrative o F several
aspects of the invention.
Two heats of steel were cast and processed into
:':1
silicon stee] having a cube-on-edge orientation. The chemistry
of the heats appears hereinbelow in Table 1.
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Composition~wt. ~o) . . .
Heat C Mn _ Si S Al N _F e
A 0. 05 0.11 2. 92 0. 03 0. 023 0. 0055 Bal.
S B 0. 053 0.13 2. 85 0. 031 0. ~23 0. 0055 . Bal.
Processing for the heats invol~ed soakina at an elevated temperature for
~everal hours, hot rolling to a gage of approximatel y 93 mils, T~ormalizing~
cola rolling to a fiTlal gage of approximately 12 mils, decarburizirlg at a
temperature of 1475F in a mixture of wet hydrogell and nitrogen, applying
10 one of four base coating ~, and final texture annealing at a maxirnum
temperature of 21 50~:F . The four base coatings are as follows:
: I. 100 parts MgO
; II. : 100 parts MgO ~ 2 parts H3BO3 ~ ;
,
IIt. 100 parts MgO + 2 parts H3BO3 ~ 4 parts 1~H4)2S04
15IV. 100 parts MgO + 4 parts (NH4)zSO4 ~:
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The heats were tested for permeability and core loss. Results
of the tests appear herelnbelow in Table II. Note that the results are
arranged so as to reflect the base coating used. :
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TABLE II
: 20 ~ _ Heat A Heat B ~ ;
Permeability Core Loss Permeability Core Loss
(WPP at 17KB) (at 10 O ) (WPP at 17KB~ -
I. 1863 0. 787 1826 0. 860 ~ -
I. 1911 ~ 0. 698 1885 0. 75~ :
III. 1943 0. 657 }879 0. 705
,~ :
2SIV. ~ 1933 0. 679 1919 0. 680
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~55368
From t5~e results appearing in Table II, it is clear that the inclusion
of ~NH4)2S04 in the base coating improved texture development. Steels coated
with coatings IV and III had respectively higher permeabilities and lower
core loses than did steels coated with coatings I and II. Coatings IV and IlI
5 contained tNH4)2S04 whereas coatings I and II were devoid thereof.
It will be apparent to those skilled in the art that the novel
principles of the invention disclosed herein in connection with specific `
examples thereof will suggest various other modifications and applications
of the same. It is accordingl,v desired that in construing the breadth of
' 10 the appended claims they shall not be limited to the specific examples of the
invention described herein.
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