Note: Descriptions are shown in the official language in which they were submitted.
~04~9
1 The present invention relates to a process for
producing electromagnetic silicon steel having a cube-on-edge
orientation and a permeability of at least 1850 (G/Oe) at
10 oersteds.
Oriented silicon steels containing 2.60 to 4.0%
silicon are generally produced by processes which involve hot
rolling, a double cold reduction, an anneal before each cold
roll and a high temperature texture anneal. Characterizing
these steels are permeabilities at 10 oersteds of from about
1790 to 1840 (G/Oe).
- In recent years a number of patents have disclosed
methods for producing silicon steels with permeabilities in ~ -
excess of 1850 (G/Oe) at 10 oersteds. Of these United States
Patent Nos. 3,287,183, 3,632,456 and 3,636,579 appear to be the
most interesting. A still more interesting method is, however,
1 described in a United States patent. The patent is U.S. Patent
j No. 3,855,020 which issued December 17, 1974 in the names of
James A. Salsgiver and Frank A. Malagari. Patent 3,855,020
describes a process 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 0.07% sulfur, from 0.015 to 0.04% aluminum, up to
0.02% nitrogen, from 0.1 to 0.5% copper, balance iron; casting ~ ~-
the steel; hot rolling the steel; annealing the steel prior to -~
!t a final cold roll at a temperature of from 1400 to 2150F; -
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cooling the steel from a temperature below 1700F and above -,~
i 750P to a temperature at least as low as 500F with a liquid
f quenching medium or gaseous stream and from its maximum annealing
temperature to the temperature below 1700F and above 750F at
a rate which i8 no faster than one wherein the stee1 is cooled
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10418~79
1 in a static atmosphere or in a continuous processing line
where there is some relative motion between the atmosphere and
the steel, although the only deliberate motion is that imparted
to the steel; and cold rolling the steel at a reduction of at
least 80%.
Described herein is another, and improved method for
producing silicon steel having a cube-on-edge orientation and a
i permeability of at least 1850 (G/Oe) at 10 oersteds. It is
3 primarily based upon the discovery that the melts of above
mentioned U.S. patent 3,855,020 with another D.S. Patent No.
3,925,115 which issued to the applicant on December 9, 1975
can be prepared with boron added thereto. Boron has been
successfully used to help develop high permeability in grain
oriented silicon steels. It is primarily based upon the dis-
covery that the melt of U.S. Patent 3,855,020 can be prepared
with selenium replacing part or all of the sulfur contained
therein.
It is accordingly an object of the present invention
to provide a process for producing electromagnetic silicon steel
having a cube-on-edge orientation and a permeability of at
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j least 1850 (G/Oe) at 10 oersteds.
-
The present invention provides a method for producing
? silicon steel having a cube-on-edge orientation and a permeability
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of at least 1850 (G/Oe) at 10 oersteds. Involved therein are
~ the steps of: preparing a melt of silicon steel consisting
j essentially of, by weight, up to 0.07~ carbon, from 2.60 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,
rom 0.015 to 0.04% aluminum, up to 0.02~ nitrogen, from 0.1 - -
to 0.5% copper, from 0~00045 to 0.0035% boron, balance iron;
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10418~79- 1 casting the steel; hot rolling the steel into a hot rolled band;
subjecting the steel to at least one cold rolling; subjecting
the steel to a final annealing prior to the final cold rolling;
decarburizing the steel; and final texture annealing the steel.
Also included, and significantly so, are the specific steps of:
carrying out the final anneal prior to the final cold rolling
at a temperature of from 1400 to 2150F for a period of from 15
seconds to 2 hours; cooling the steel from a temperature below .
1700F and above 750F to a temperatuxe at least as low as 500F
with a liquid quenching medium or gaseous stream and from its
maximum annealing temperature to the temperature below 1700F
~', and above 750F at a rate which is no faster than one wherein the - .
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steel is cooled in a static atmosphere or in a continuous processing line where
there is some relative motion between the atmosphere and the steel, although
the only deliberate motion is that imparted to the steel; and cold rolling the
cooled steel at a reduction of at least 80%. Preferred conditions include
annealing at a temperature of from 1800 to 2125F~ cooling with a liquid
quenching medium or gaseous stream from a temperature below 1600F and
above 1000F, and cold rolling at a reduction of at least 85%.
Melting, casting, hot rolling, cold rolling, decarburi ing and final
texture annealing do not involve any novel procedure, as far as techniques!are
0 concerned, and with regard to them, the invention encompasses all applicable
-` steelmaking procedures. As to the cold rolling, it should however, be pointed
, out that several roll passes can constitute a single cold rolling operation, and
1 that plural cold rolling operations exist only when cold rolling passes are
separated by an anneal.
I5 Jn addition to boron, the steel melt must include silicon, aluminum,
- manganese, and sulfur and/or selenium, Silicon is n~ecessary as it increases ~ -
the steels' resistivity, decreases itq magnetostriction, decreases its
magnetocrystalline anisotropy and hence decreases its aD re loss. Aluminum, - -
manganese, and sulfur and/or selenium are necessary as they form inhibitors
~0 wh*h are essential for controlling the steels' orientation and its properties
wh~ch ire depende~t thereon. More specifically, aluminum cornbines with
n~trogen in the steel or from the atmosphere, to form aluminùm nitride; and
mangane~e combines with sulfur and/or selenium, and possibly copper, to form
- manganese.sulfide and/or manganese copper sulfide and/or manganese selenide
~25 and!or sn~Lngane~e copper salenide, All together, these compounds Lnhibit
normal grain growth during the final texture anneal, while at the same time
a~d~ng in the development of ~econdary recrystallized grains having the desired
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cube-on-edge orientation, Copper, noted dbove for its presence in manganese
inhibitors, can also be beneficial during processing. It is hypothesized that
copper can lower the annealing temperature, lower the temperature frorn which
the rapid cool can occur, improve rollability, ~implify melting, and relax
S annealing atmosphere requirements. Moreover, copper increases the steels'
resistivity and decreases its D re loss,
A steel in which the process of the present invention is particularly
adaptable to consists essentially of, by weight, from 0.02 to 0.07% carbon, from2 . 65 to 3. 2 5~o silicon, fro m 0, 0 5 to 0 . 20 % mangane se, from 0 . 02 to 0 . 07% of
~10 material from the group consisting of sulfur and selenium, from 0.015 to 0.04%
aluminum, from 0.0030 to 0.0090%nitrogen, from 0.1 to 0.4% copper, from - -
0.0005 to 0.0025% boron, balance iron. This steel has its chemistry balanced
~o as to produce a highly beneficial structure when processed according to the
present invention. As a general rule boron contents will be in excess of
0. 0007%. -
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` Although we are not sure why the final a,nneal prior to the final cold -
-~ rolling, and the controlled cooling of the present invention is so beneficial, we
hypothe~ize: that the anneal conditions the steel for cold rollilg and providean operation during which inhibitors car. form; and that the slow cool to a
temperature below 1700F and/or the use of annealing temperatures in the
lo~er part of the annealing temperature range, increase the uniformity in
which the inhibitor3 are distrlbuted, as essentially only ferrite phase i~ -
pre~cnt in the steel at temperatures below 1700F, contrasted to the presellce
of au~tenite and ferrite phase~ and different solubilitics for the inhibiting
,
elemeslts in each phase at somewhat higher temperat ures, As discussed above,
the prirnary i~hlbitor~ are aluminum nitride, and compounds of manganese
~u14ide and mangane~e selenide, No criticality is placed upon the particular
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~041879
anne:~ ing atmosphere. nlustrative atmcspheres therefore include nitrogen;
reducing gases such as hydrogen; inert gases such as argon; air; and mixtures
thereof .
The following examples are illustrative of several aspects of the
invention.
Four heats of steel were cast and processed into silicon steel having
a cube-on-edge orientation. The chemistry of the heats appears hereinbelow
in Table L - -
TABLE L
. '
~0 Composition (wt. %)
Heat C Mn Si S Al N Cu B Fe
, A 0.045 0.11 2.840.0350.0300.0078 0.20.00048Bal. i -~
B 0.046 0.11 2.850,0360,0290.0065 0.20,00078Bal.
C 0.046 0,11 2.830.0350.0300.0062 0.190.00141Bal.
D 0.046 S). ll 2.840.0350.0300.0064 0.20.00226Bal.
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Processing for the heats involved soaking at an elevated temperature for ~ -
soveral hours, hot rolling to a gage of approximately 93 mils, heat treating for
1 minute at 2050F, slow cooling to 1740F (approximately 50 seconds), air
-. cooling to 1100F, water quenching from 1100F, cold rolling to a final gage of
~0 approximately 12 mils, decarburizing at a temperature of 1475F in a mixture
'A;' of wet hydrogen and nitrogen, and final texture annealing at a maximum
s ten~perature of 2150 F.
TSe heat~ weré te~tod for permeability. Respective permeabilities - -
of 1906, 1889, 1873 and 1898 (G/Oe) at 10 oersteds were recorded.
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10418~9
~ w~ e apparer.t Lo those skilled in the art that the novel
principles of the invention disclosed herein in connection with specific exarnples
thereof will suggest various other modifications and applications of the same.
It is accordingly desired that in construing the breadth of the appended
claims they shall not be limited to the specific examples of the invention
described herein,
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