Note: Descriptions are shown in the official language in which they were submitted.
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1 ABSTRA~T OF THE DISCLOSURE
A me~hod for producing grain oriented silicon s~eel
: wherein the steel may be hot rolled directly from ingot to hot
band at lower than conventional temper~tures without adversely
affecting the magnetic properties thereof. In addition, the
steel i characterized by a manganese to sulur ratio less than
about 2.5 and preferably about 1 to less than about 2.5. Hot
rolling is conducted at a temperature of less than 2300F and
preferably 2200 to less than 2300F. Preferably the steel
co~tain~ copper in an effec~i~e amount up to 0.4~ by weight and
preferably about.O.2 to less than 0.58% by wei~ht.
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Grain oriented silicon steel in the form of sheets is
known for use in variou~ elec~rical applica~ions, inclu~ing ~he
,manufacture of transformer cores. The ste~l is produced by
~. . .
ingot casting, heating the ingot, typically in gas-fired soaking
pi~s, ~o a temperature suitable for ho~ rolling either to the
form o a slab or directly ~o hot band~ The hot band, after
~nne~line a~d pi~kl ;n~ iS cold rolled in one or more stages
with inter~di~te annealIng. The steel is then normalized during
which decarburization is achieved. Thereafter, it is subjected
to a firlal texture annealing, wherein the desired crys~al
orientation is achieved. Conven~ionally, when rolled directly
from -ingot to hot band the ingot ~emperature is on the order of
~450F.
During final ~ex~ure annealing the si].icon steel under
goes secondary recrystallization where the aggregate of grains
grow and have cube-on-edge or (110) [001] orien~ation or ~ex~ure.
'
~e377~
- 1 lnese large grains have ~heir [OOlJ axes parallel ~o the roll-
ing direction and (110) faces p~rallel to ~he rolli~g plar.~.
hus, the materi21 which is in shee~ form, has 2 single
direetion of easy magnetization, in the direction of rolling.
In applications for US2 of this material, and speci~.ically ~ en
used in the manufac~ure of transformer cores, the material is
required to have low core loss, beeause the consumption of
thermal energy decreases as core loss decreases. In addition,
for ease of magne~ization ~he s~eel should be charaeterized by
good m~gnetic permeability.
To achieve these required magnetic properties, e.g.
core loss and magnet~c permeability, it has been necessary ~o
hot roll at an ingot ~emperature on the order of 2450F.
Co~seq~e~tlys the coL,~.L ional practice is ~o hot roll from
lS ingot or sla~ to hot band at te~pera~ures above about 2300~F
and up to abou~ 2550F. These extremely high ~emperatures,
however, are ~i~ff ~ult t~ work wlth and specifically cr~ate
probLe~s with disposal of slag which forms during ingot heating
to ~hese hi:~h temp~ratures in ~he soaking pit. Also, ~he high
. . .
2D hea~ing requirem~ts add ~o ~he energy cos~s o the ov2rall
oper tion, i~ addition ~o incrc2sing the refrac~ory costs of
the heating apparatus.
It i~ accordingly a prim~ry objeet of ~he presen~
i~vention ~o pro~ide a method for producing g~ain orien~ed
silicon steel ~herein lower than conven~ional ho~ rolling
; ~emperatures m~y be used without adversely affecting ~he
magnetic properties of the steel, principallv core loss a~d
agnetic permeability.
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-2
1 This and other objects of the invention, as ~lell as
a more complete understanding thereof, may be obtained from the
following description and specific examples.
Broadly, in accordance with the practice of the
invention, grain oriented silicon steel of otherwise conventional
composition may be hot rolled d1rectly from ingot to hot band,
which hot band typically has a thickness of about 0.1" or less,
if said steel has a manganese to sulfur ratio of less than
about 2.S and preferably a manganese to sulfur ratio within the
range of about 1 to less than about 2.5. Preferably, in
accortance w~th the in~en~ion hot rolling is conducted with a
s~eel having a manganese to sulfur ra~io in accordance with -the
above wi~h said ingot a~ a ~emperature of 2200 to less ~han
2300F. It has been found, as will be demons~rated hereinafter
by way of specific examples, ~hat these lower than normal hot
rolling tcmperatures will not adversely affect ~he eore loss
and ma~netic permeability of the steel if the aforementioned
low mangane5e to sulfur ratios a~e adhered to. Further, in
aecordance with the in~en~ion, the core loss values may be
further improved i the steel contains copper in an effeotive
amount up to about 0.4% by weigh~ and preferably about 0.2 to
less than about 0.58% by weigh~. Hence, in hot rolling direc~ly
from ingot to hot band optimum core loss and magnetic
permeability values are ob~ained if ~he s~eel is characterized
by both the low m~n~ne~e to sulfur ratios set for~h hereinabove
as well as cont~in;ng copper within the prescribed amounts. If
these teachings of ~he invention are followed the relatively
high hot rolling temperatures conventionally necessarv to
achieve good magnetic properties are no longer required.
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1 Cc-.sequentl~, b~ the use of lower ~.an nor~.al .olli~g
-e=?~râtu-es .he disadvant2ges fro~. the processing a~.~ c-s
S G?.d?Oin~ as discussed hereinabc~Je ~.-a~ be avoideG. ~ re~o-~
the invention provides a practice ;~herein a graln orie~.~e~
silicon steel may De produced ha~-ing good ~agnetic p~o?e-ties
at significan~ cost advantage over conventlcnal practice. ~-
way of specific example, and specifically to demonstrate ~ne
significance o manganese to sulrur ra~ios in accordance wi~h
the invention on the magnetic properties of the steel, the
following silicon steel com~ositions as set forth in Table I
were p~oduced and hot rolled within the range of 2200 to 2300F
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TABLE I
10.8 ~lil
Magnet ic
Quality
HR WPP
Heat C ~ S Si Al Gu B Mn Temp, F 17KB ~lQH
63~1 .030 .038 .035 3 u 04 .005 .20 . ~004 1.10 2200 .758 1854
6352 .030 .040 . ~36 3. ~5 .005 .1~ .0004 1.10 2200 .755 1850
6344 .030 .043 .035 3.00 .00~ .20 . OG04 i .20 2200 .772 1864
~345 . Q~8 .042 .035 3. oa . oo~ .20 .0004 1.20 2200 .753 1~58
6341 .030 .042 .034 2.95 .005 .20 .0005 1. ?3 2250 .761 1845
6168 . ~33 .049 .030 ~ .12 .004 . i8 .0007 ~ .6~ 23QO .704 1845
9 .0~0 .055 .023 3.1~ .004 .18 .0~04 2.4~ 2300 .7Q4 1812
~16~ .04~ . ~65 .0~0 3.00 .0~ .20 .0~10 3.25 2300 .882 1693
1 . The ste~ls as set forth in Table I were hot rolled
directly from ingot to hot band with the hot band having a
thickness on the order o 0.080 to 0.090". The ho~ band was
annealed at 1650F.and cold rolled to an in~ermediate thickness
of .028 to 0.030l'. The intermPdiate gage strip was annealed
a~ a temperature of 1740F before cold rolling to a final gage
o~ 0.108".
As may be seen from Table I, the core 19ss values
(WPP, 17KB~ are improved for the steels having manganese to
sulfur ratio~ less than 2.5 over steel Hea~ No. 6162 having a
relatively high manganese to sulfur ratio of 3.25 which is
typical of conventional steels of ~his type.
The effec~ of copper with respec~ to further improv-
ing core loss is shown by the heats reported on Tabl~ II.
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.
TABLE II
10 . 8 Mil
MgO- Coated
Ma~;ne~ic Qual ity
HR WPP
He~t C ~ln S Sl Al Cu B ~ O S - Temp, F 17KB ~10ll
6369 . ~34 . ~39 . 022 3 . O . ~5 . ~9 . 0006 1 . 8û 2250 . 73~ 1~6(~
6370 . 031 . 042 . 022 3 . ~ . 0~5 . 4~ . O~Q5 1 . 90 225~ . 721 1~6
6364 . 030 . 04~ . 026 3 ~0 . Oû5 . 58 . aoo7 l . ~5 2250 . 768 -1849
6433 . 030 . 042 . 022 3 . O . ~05 . 20 . 0û14 1 . ~1 2250 . 710 1869
~37 7 . 028 . 042 . Q21 3 ~ O . 005 . 42 . 0009 2 . 00 2~50 . 71 9 1874
6 3 7 6 . Q~9 . 047 . 074 3 . O . ~5 . 58 . 0009 1 . 96 2~50 . 763 1843
The-steeIs reported on Table II we~e hot rolled
directly from ingot to hot band having a thickness o~ O . 090" .
The hot band was cold rolled to inal gage in two stages with
.~ a~ intermediate anneal. Initial annealing, prior to cold
rolling, was at a temperature of 1650F whereupon the material
was rolled to a thickness of 0.028"; 1~ was then annealed at a
: temperature of 1740F and rolled to a thickness o 0.0108".
: The material was ~hen final normalized at a tempera~ure of
1475F during which deearburization was achieved. Finally,
~he decarburized strip was conventionally coated with magnesium
oxide and annealed in a hydrogen atmosphere of 2150F. As may
.~ be seen from the core loss values (WPP 17KB) repor~ed in
. , .
Table II the presenCQ of copper in an amount above about 0.2%
as shown by the ~t el identified as Heat 6370 shows improved
core loss over steel iden~ified as Heat No. 6369 having 0.19%
r copper. The core los~ values deteriorate, hcwever, if copper
is not maintained a~ a~leYel less than about 0.58%, as m~y be
seen from the steel identified as Heat No. 636h, which shows
a significant deterioration in core loss at a copper con~ent
.~ 20 O~ 0,5~V/4,
.~ :
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