Note: Descriptions are shown in the official language in which they were submitted.
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The pre~ent Lrl~c.ntio:l -elateY to a process for p.odlcln~
20 electromagnetic silicon steel having a cube-on-edge orientation and a
perrneability o~ at least lS50 (G/Oe) at 10 oersteds.
Oriented silicon s,.eel~q containing 2.60 to ~L.0~o 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.
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1 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 ~ilicon 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, described in the
applicant's United States patent 3,855,020 which issued December
17, 1974. U.S. patent 3,855,020 describes a process which includes
the steps of: preparing a melt of steel consisting essentiall~
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 0.0~5 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 a final cold roll at a temperature o~ ~rom
1~00 to 2150F; cooliny the steel from a temperature below 1700F
and above 750F to a temperature at least as low as 500~F with a
liquid quenching medium or gaseous stream and from its maximum
annealing temperature to the temperature below 1700F and above
20 750F at a rate w~ich is no faster than one ~herein the steel is :
cooled in a static atmosphere or in a continuous processing line
where there is somQ relative motion between the a~mosphere and thQ
steel, although the only deliberate motion is that imparted to the
steel; and cold rolling the ~teel at a xeduction o~ at lea~t 80~.
Described herein is another, and improved method
for producing silicon stQel having::a cube-on-edge.orient-
tat~on and a permeability of at least 1850 (G/Oe) at 10
oersteds. It is primaril~ based upon the discovery that the
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~ melt of ~ -r4 can be prepared with selenium replacing part
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or all of the sulfur cont~ined therein,
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 least 1850 (G/Oe) at 10 oersteds.
The present invention provides a mel;hod for producing silicon steel
having a cube-on-edge orientation and a permeal~lity of at least 1850 (G/Oe)
at 10 oersteds. Jnvolved therain are the steps of: preparing a melt of silicon
steel collsisting essential,~y of, by weight, up to 0. 07% carbon, from 2, 6d tolû 4.0% silicon, from 0.03% to O.Z4% manganese, at least 0.01% selenium, 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, from 0.1 to 0. 5% copper,balance iron; 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 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 lS seconds to 2 hours;
cooling the steel from a temperature below 1700 F and above 750 F to a
2û temperature at lea~t a~ low a~ 500 ~F with a liquid quenclling medium or gaseous
~tream and from its maximum annealing temperature to the temperature below
1700~F and above 750F at a rate which i9 nofaster than one wherein the 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 mo-tion i9 that imparted to the steel; and cold rolling the cooled
steel at a reduction of at least 80%, Preferred conditions include annealing
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at a temperatur~ of from 1800 to 2125F, cooling with a liquid quenching
mcdium or gaseous strean~ from a temperature below 1600~F ~nd above 1000F,
and cold rolling ~t a reduction of at lea~t 85%.
Melting,casting, hot rolling, cold rolling, decarburizing and final
S texture ann~aaling do not involve any novel procedure, as far as technqiues are
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 operationJ andthat plural cold rolling operations exist only when cold rolling passes are
separated by an anneal.
The steel melt must include silicon, aluminum, rnanganese and
~elenium. Siliconis necessary as it increases the steel's resistivity, decrcasesi1:s magnetostriction, decreases its magnetocrystalline anisotropy and hence
decreases its core loss. Aluminum, manganese and selenium are necessary
~15 as they form inhibitors which are essential for controlling the steel's
orientation and its properties which are dependent t~;ereon. More specifically,
alumxnum combi~es with nitrogen in the steel or from the atmosphere, to
form alurninum nitride; and manganese combines with selenium, and possibly
copper, to form mangane9e sclenide and/or manganese copper selenide, and
Z0 with ~ulfur if it is present, to form manganese sulfide and/or manganese copper
~ulfide. All together, these compounds inhibit normal grain growth during the
final texture anneal, while at the same time aiding in the development of
~econdary recrystallized grains having the desired cube-on-edge orientation.
Copper, noted above for its presence in manganese inhibitors, can also be
beneficial during proces~ing. It is~ hypoShesized that copper can lower the
annealing temperature, lower the temperature from which the rapid cool can
occur, improve rollability, simplify melting, and relax annealing atmosphere
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requirernent~. Moreover, copper increases the ste~ls' resistivity and
decreas e s its c or e lo~ ~,
A steel is~ which the process of the present invention is particularly
adaptable to consists essentially of, by weight, from 0 02 to 0.07% carbon,
from 2. 65 to 3. 25% silicon, from 0. 05 to 0. Z0% mang~nese, at least 0. 02%
selenium, from 0~02 to 0,07% of material from the group consist~ng 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, balance: iron. This steel has its chemistry
balanced so as to produce a highly beneficial structure when processed
according to the present invention.
Although we are not sure why the final anneal prior to the final cold
rollingi and the controlled cooling of the present invention is so beneficial, we
hypothesize: that the anneal conditions the steel for cold rolling and provides
an operation during which inhibitors can form; and that the slow cool to a
temperature below 1700F and/or the use of annealing temperatures in the lower
part of the annealing terrlperature range, increase the uniformity in which the
inhibitors are distributed, as essentially only ferrite phase i9 present in the
steel at temperatures below 1700F, contrasted to the presence of austenite
and ferrite phases and different solubllities for the inhibiting elements in each
phase at somewhat higher l:emperatures, As di9cu9sed above, the primary
inhibitors are aluminum nitride, and compounds of rnanganese selenide asld
pos~ibly manganese sulfide, No criticality is placed upon the particular
annealing atmosphere, ~lustrative atmosphere therefore incLudenitrogen;
reducing gases such as hydrogen; inert gases such as argon; air; and mixtures
thereof.
The follow~ng example is illustrative of several aspects of the
invention.
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A he~ of steel ~as cast and processed into ~ilicon ste~l having
a cuoe-on-edge orientation. The chemistry of the heat ap~2ars hereinbelow
in the Table.
TABLE
Compos ition (wt. %) ~
_ C Mn SiSe S Al Cu _ N Fe
0.066 0.13 2.77 0.0S6 0.013 0.028 0.4 0,0068 Bal.
Processing for the heat involved soaking at an elevated temperature for
several 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
c)f approximately 12 mils, decarburizing at a temperature of 1475F in a
mixture of wet hydrogen and nitrogen, and final texture annealing at a maximum
temperature of 2150F.
The heat was tested for perrneability~ A permeability of 18S3
(G/Oe) at 1~ oersteds was recorded.
s
It will be apparent to those skilled in the art that the novel
principles of the invention disclosed herein in connection with specific example~
thereo~ will suggest various other modifications and applications of the same,
20 ~t i~ accord~ngly 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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