Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to the art
of producing electrical ~teel and is more particularly concerned
with a novel method of producing ~ingly-oriented silicon-iron
sheet through the use of ~mall but critical amounts of boron,
and with a new cold-rolled silicon-iron sheet product.
This invention is related to the invention disclosed
and claimed in U.S. patent No.~3 ~/DSJ ~ y~ issued
5e~t~A'~r/~/Ç~s , entitled "Method of Producing Oriented
Silicon-Iron Sheet Material With Boron Addition" in the na~e
of ~oward C. Fiedler and a~igned to the assignee hereof,
dir-cted to the novol concept of cold rolling hot-rolled ~ilicon-
iron sheet direetly to final thiekness without an intermediato
-~ heat treat~ent through the u~e of small but eritical amounts
of boron and by maintaining the ratio of manganese to sulfur
in the metal at les~ than 1.5~
The invention disclosed and claimed herein also
relate~ to that diselosed and elai~ed in U.S. Patent No.
~- 3,~ , issued ~ ~ t~ 6 , entitled ~Method of
Producing Oriented Silicon-Iron Sheet ~aterial With Boron
AdditionU in the na~e of Howard C. Fiedler and as~igned to the
assignee hereof, whieh pertains to the new eoneept of using
small but eritieal amounts of boron to enable the produetion
of singly-oriented ~ilieon-iron sheet of improved magnetie
properties by ~ubjeeting ~ilieon-iron sheet eontaining manganese
and sulfur in a ratio less than 2.1 to a eold reduetion ~eguence
ineluding an int~nmodiate annoaling step and 2 final heavy eold
rolling reduetion.
Tho ~heet materials to whieh this invention is direeted
are u~ually referred to in tho art as ~eleetrieal~ ~ilieon
~teels or, moro prop-rly, ~ilieon-irons and are ordinarily
eompo~ed prineipally of iron all~yad with about 2.2 to 4.5
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per cent ~ilicon and r~lativoly minor amount~ of variou~
i~puritie~ and very ~mall amountJ of carbon The~e product~
ar~ of the "cube-on-edge~ type, ~ore th~n about 70 por cent
of thsir cryatal ~tructure being oriented in the (110) 00
toxture, as de~cribed in Miller Indice~ ter~s
Such grain-oriented ~ilicon-iron ~heet products are
currently made com~ rcially by the sqquence of hot rolling,
heat treating, cold rolling, heat treating, again cold rolling
and then final he~t treating to decarburize, de~ulfuriz- and
recrystallize Ingots are convontionally hot-worked into a
strip or sheet-like configuration le~8 than 0 150 inch in
thickne-~, referrod to as Uhot-rolled band " The hot-rolled
band i~ thon cold rollod with appropriate intermediate ann-aling
treat~ent to the finished sheet or Jtrip thicknes~ u~ually
Lnvolving ~t l~ast a 50 p-r ce~t roduction in thickne-s, aad
giv~n a final or texture-producing annealing treatment
I hava discover-d that under certain conditions boroa
ha~ a b neficial effect on the ~econdary recrystallization of
si}icon-iron sh -t ~atorial to dov-lop the (110) LOO~ textura
and the ~p~cial magnotic properti-~ a~ociated with it
; Particul~rly, I have found that th proaence of a vory snall,
but highly ~ritical, amount of boron in cold-rolled Jilicon-
iron ~heet during the final or texture-developing anneal enable~
preparation of ~ilicon-iron sheot having a Jtrong cubo-on-edge
textur- and corre-pondingly good magnetic propertie~ In other
`- word~, the seemingly insignificant amount of boron ~akes
secondary recry~tallization possible Conseguently~ the u~e
of ~angane~e sulfide can be avoided as can the neces~ity of
a high-temperature de~ulfurizing heat treatmeat during the
final processing operations Thu3, the metal can by reason
of this invention be desulfuriz~d at the melt stage with
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~ub~tantial time and co~t ~aving~. All thi~ i~ quite ~upris-
ing considering the f~ct that boron hAs previou~ly been
recognized in our experience a~ a detrimental impurity which
it definitely i8 in amounts only moderately greater than those
which I have found to be useful. In fact, ~xcept $n the
pre~ence of otherwise detrimentally high amount~ of nitrogen
in the metal, boron in amount a~ small as 50 parts per
million (ppm) is definitely detrimental in terms of desired
magnetic characteristics. ~hus, the important new re~ults and
advantages of this invention are obtained through the presence
of boron in amounts from about five to about 45 ppm during
the texture anneal of the cold-rolled sheet. I h~ve found
the optimum boron content to be in the range from about five
to 20 ppm.
This unigue capability of bDron wa~ discovered during
experiments involving the use of crucible refractories contain-
ing boron a- a minor impurity. ~ all amounts of boron were
reduced from the rofractories to the silicon-iron melts and
exerted noticeable beneficial effect on the texture-developing
processO Subsequently, I demonstrated that the boron content
in silicon-iron melts prepared in such vessels could be closely
controlled by ad~usting the melt carbon content as by adding
iron oxide and thereby preventing the reduction of boron in
the crucible refractory and consequent pick-up of boron by
the melt. I further found that the boron requirements can be
m~t through the use of a boron-free crucible by adding a boron
source to the melt.
I have further found that the surprisingly ~harp
criticality of such relatively ~mall proportions presents no
substantial difficulty in either laboratory or mill~cale
operations. Thus, boron in suitable form i-~ added in requi~ite
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amount to the melt shortly befor~ ca~tinq. In mill practice,
the boron JOUrce i~ suitably add~d to the ladle after the
u~ual ferrosilicon addition. No significant lo~ of boron
from the ~etal occur~ through hot and cold rolling and heat
treating stages prior to the final heat treatment. Ho~ever,
boron 108~ c~n bo substantial if the boron source is added
well in advanco of ca~ting or if the ingot is ~oakod at high
tonperature for a prolonged period. During the final anneal,
es~entially all the boron i~ eliminated from the metal when
in accordance with thi~ invontion the role of boron in promoting
the d~ired secondary recrystallization texture develop~ont
ha~ terminated.
I have additionally discovored that the proportion of
nitrogen to boron i~ al~o of critical importance to the new
result- and advantages of this invention. unles~ the ratio of
nitrogen to boron i~ in the range-from two to four parts of
nitrogen per part of boron, products having good magnetic
propertioJ can not be consiJtently produced even though the
boron content of the melt i8 within the above stated critical
- 20 range. con~equently, in accordance with this invention, thenitrogen content of tho m lt will be in the range from about 15
part~ per million to about 95 parts per million.
The nitrogen requirement can be mot in any convenient
man~er, but in proferred practice the motal in a vacuum furnace
is provided with a 30-torr nitrogen atmosphere to which argon
i~ added to bring the pressure up to one atmo~phere for the
pouring operation. The metal as poured contains about 30 ppm
of nitrogen and in the neighborhood of 10 ppm of boron. The
pressurc of nitrogen required in the furnace chamber will dep~nd
in any given circumstance upon the ratio of the volume of the
chamber to the weight of the melt.
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1~4~7~
Anothor di~covory which I havo made is that the
proportions of ~ulfur and mangan~se in the ~etal duri~g
final ~nnealing treatment are critlcal in t~rms of the
magnetic propertie~ of the final product strip or sheet
material. Particularly, it i9 essential that there be at
lea~t 0.007 per cent ~ulfur in solute form at that stage of
proce#sing. That re~uirement can be met if both th~ ~ulfur
and the m~nga~ese contents of the ~ilicon iron are quite low
~nd in fact if there i8 no more than about 0.007 per cent
sulfur in the metal. The tendency for the manganese to tie
- up the sulfur i8 ~egligible in highly dilute systems in which
the manganose content is of the order of about 0.002 to 0.006
per cent and, conseguently, it i8 not ~ecessary in the practice
of this invention to reduce the manganese content of the metal
to a trace amount under any circumstances.
From the foregoing it will be understood that this
invention has both method and article or product aspects.
Thus, the several di~coveries and new concepts set forth above
expressed in terms of manipulative ~t~ps add up to a novel
process and when expressed in co~positional terms de~ine a
unigue silicon-iron sheet product. The product i8 a cold-rolled
sheot of final gauge thickne~s which by virtue of its boron,
nitrogen, mangane~e and sulfur content can be converted to
the oriented state in which it will have valuable magnetic
properties but will not contain the boron which enabled the
develop~ent of thoJe properties through secondary recry~talliza~
ion. The process of producing this new intermediate cold-
rolled ~heet i8 al~o new as i~ the overall process of producing
the final dosired ~heet material fro~ a silicon-iron melt.
Briefly described in its article aspoct, this
invention comprises a cold-rolled silicon-iron sheet product
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containing 2 2 to 4 5 per cent ~Llicon, between ~bout 5 and
45 ppm boron, between about 15 ~d 95 ppm nitrogen with the
nitrogen and boron being in the ratio range of 2 to 4 parts
of nitrogen per p~rt of boron, b~tween about 0 007 and 0 006
per cont ~ulfur, an~ between ~bout 0 002 and O Ol por cent
~angan-~e, and the proportion of ~angan~se to sulfur b-ing
such that the presenco in tho ~ t~l of at loast 0 007 per cent
sulfur in soluto forn is as~urod during the final textur~
anneal
Similarly de~cribed, the ~ethod co~pri~es the steps
of providing this intormediate ~hoot product and subjocting
-~ it to a final heat treatm nt to develop (llO) rOOlJ secondary
recrystallization t-xture in it
In tha preferred practice of this invontion, the
a~ount of nitrog n in th~ metal will not oxceed about 60 ppm
80 th~t any tendoncy for nitrogen-induced ~liv~ring and
bli~toring can be avoided Thi~ r~guire~ent i- ro~dily met
by con~orci~l ~teel-producing practice- when u~u~l precautions
aro taken to limit nitrogen pick-up Con~eguently, it is
pr-forable to add boron to th0 melt after it has been tapped
into the ladlo for te-~ing The amounts to be added will bo
10-20 ppm of the ~elt weight
In carrying out the ~othod this inv~ntion, ono will
pr~par- a silicon-iron melt of roquired che~i~try and U8~ it to
produce ingots whi~h are hot roll-d to interaediato thickness
When it i8 poured, tbe ~elt will contain fro~ 2 2 to 4 5 per
cent silicon, from 0 003 to 0 06 per cent sulfur, fro~ ~ 001 to
0 10 por c~nt mangane-e and from about 5 to 45 part~ per
~illion boron, fro~ about 15 to 95 parts per million nitrogen
in the ratio range to boro~ bet~e-n two and four parts to one,
the remainder being iron and sMall incidental amount~ of other
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ele~ent~ including carbon, aluminum and oxygen. The resulting
~hoet is cold rolled to final gauge thickne~ and subjectod
to the final heat treat~ent for decarburization and development
of the ~110) L ool~ 3econdAry recrystallization texture.
Preferably, hot rolling will be carried out between 1100 and
1350 C and the hot-rolled sheet will bo pickled and th-n may
be heat treated suitably for several minutes at 900C to
looo& before cold rolling. cold rolling may be in one stage
or m two stage~ with an intermediate anneal. Also, the
decarburization heat treatment at final gauge will be carried
out at 800C in hydrogen containing sufficient moisture
to effect the removal of carbon. A heat treatment of one to
five minutes is used for this purpose. In the final texture
anneal, ~econdary grain growth to produco the deRirea
t~xture i8 initiated at about 950C when heating at 50C per
hour in pure nitrogen. Recrystallization should be completed
by the time the temperature attains 1000C and a change of
atmosphere to purified dry hydrogen can then be made. Heating
can be continued to about 1025& for a low temperature anneal,
or to higher t~mperatures ~uch as 1175C for more complete
removal of residual sulfur, carbon and nitrogen.
In mill operations, the sulfur content of silicon-
iron melts normally is substantially greater than the tolerable
level in finished electrical ~teel sheet products. Accordingly,
taking full advantage of ~he unique opportunity afforded by
thi3 invention for use of a lower sulfur content during the
texture-developing stage of the final heat treatment, one will
~ubject the melt to a desulfurization step. Preferably, this
i8 accomplished in the ladle prior to teeming through the
addition of lime and fluorospar to the ladle ~o that the sulfur
content of the metal is reduced to a level nearer the limit
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specified for the ultLmate sheet product.
The ~ollowing illustrat:ive, but not li~iting,
exa~ples of ~y novel method as I have actually c~rried it out
will further inform tho~e skilled in the art of the nature and
special utility of this invention:
EXAMP~E I
A vacuum furnace was used to prepare a silicon-iron
melt of tho following compositions
Silicon 3.25 per cent
Sulfur 0.009 per cent
Mang~nese 0.002 per cent
carbon 0.021 per cent
Boron 13 parts per million
;~ Alu~i~u~ 32
Nitrogen 32 u n
Oxyge~ 23 n ~ n
Iron Ro~ainder
The furnace was charged with electrolytic iron and
a carbon addition and the melt wa~ held in the ~olten condition
.:
for as long as one hour to enable reduction of boron from the
crucible. Tho ferrosilicon, ferrous sulfid- a~d a final carbon
addition were added and the melt was poured to produce an
ingot (11 x 5-1/2 x 2-5/8 inches). ~he ingot was heated to
1325C ~or 45 ~inutos under a hyd~ogen atmosphere and then
hot rolled to a sheet of about 0.085 inch thickness using
eight pa-Jo- without reheating. Pieces were cut fro~ the hot-
roll~d sheet for reduction by cold rolling after pickling to
r~ovo hot-rolling ~cale and normalizing for five ~inute~ at
goo& in hydrogen (d~wpoint about 0F). The ~heet wa~ cold
rolled without tension to 0.028 inch thickne~s and then
nor~alized three minute~ at 90~C in hydrogen (dewpoiat about
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1~4;~7~8
OOF) and again cold rolled tbut with tension) to 0.011 ifich
thickne~ est ~trip~ 3 cm by 30.5 cm in ~ize wer~ sheared
in the rolling direction fro~ this ~trip, ~ufficient to form
an Ep~tein te~t pack. Tho ~trip~ were decarburized by hoating
for three minutes at 800C in wet hydrogen (+70F dewpoint).
They were then annealed a~ a pack by heating at 50C per
hour in purified nitrogen to 975C, th-n in purified hydrogon
at the ~ame rate of heating to 1024 C, holding three hour~ at
this temperature followed by cooling at 50C per hour in
hydrogen to 600 &. From 600C to room temperature, cooling
wa~ acco~pli~hed by withdrawal o~ ~he retort to the cooling
zone of the furnaco. Magnetic te_t result~ are given below.
When this 8ame pack wa~ reannealed, heating in hydrogen to
1175C, magnetic properties were only slightly improved.
Thu~, a ~aterial requiring only a relatively low te~perature
anneal to develop good magn-tic guality i8 demonstrated.
M-qn tic ProvertieR
A.C. Los~
Thickness at ~O Hertz
~eat Treatment (mil~) 15,00B 16,300B ~lOH
1025C anneal10.7 0.537 0.647 1856
1175C reanneal 10.7 0.529 0.644 1862
EXAMPLE II
Following the procedure described in ESa pl- I, the
silicon-iron melt of the following composition was prepared:
Silicon 3.28 per cent
Sulfur 0.OO9 n
Manganese 0.002
Carbon 0.024 "
Boron 6 parts per million
Aluminum 47 parts per million
Nitrogen 27 n
Oxygen 18 " " "
Iron Remainder
_ g _
.
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Again, as in Example I, the resulting ingot was hot
rolled and otherwi~e processed a3 described therein with the
result that a product wa~ obtained corresponding to that of
Example I having permeability of 1865 gaus~es per oer~ted (in
a l0-o~rsted field), and 1088e8 of 0.553 and 0.665 watts per
pound at 15,000 and 16,300 gau88e~, respectively, following
ann~al at 1025 C.
~XAMPLE III
In th~ preparation of the melt for this example, a
change was made fro~ the method of Examplo ~. The melt was
held in the crucible in molten condition for only a few
minutes in order to limit the reduction of boron from the
crucible. A boro~ additDn~as a 19 per cent grade ferroboron
was made to the ~elt after the forrosilicon, ferrous sulfide
and final carbon additions had been ~ade. Tho resulting
compo~itio~ as determi~ed by analysis was as follows:
Silicon 3.25 per cent
Sulfur 0. 008 n
Manganese 0,003 n n
Carbon 0. 02 ~ n
Boron 12 parts per million
Nitrog~n 37 ~ u N
Oxygen 30 "
Iron Remainder
The procedura for hot rolling was ~odified from that
of ~xample I in that the rolled billet at one and one-half inch
thickness was coolod to room temperature and divided into
sev~ral pieces. The~e were reheated to one of several
te~peratures, used to continue hot rolling to 0.08 inch thick
~heet. For the material of this example, a 1300& roheat
temperature wa~ used. The total number of pas~e~ and the
. - 10 -
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roduction for each pa~ were unch~nged.
Cold rolling w~ c~rrled out in two 8tago8 with an
intermediate thic~ne-~ of 0.05 inch. The int~rmediate h ~t
treatm~nt was ~t 900C for thre~ ~i~utes in dry hydrogen as
bofore. After cold rolling to ~ f~n~l thickness of 0.011
inch, ~p~toi~ ~trip~ wore cut, dec~rburized at 800C in
hydrogen of roo~ te~perature dewpoint, and anneal~d a- in
Ex~ple I. Magnetic test value~ after ~nnealing at 1025C,
and again ~t 1175& were aq follows:
Thickn~s~ A.C. Loqa at 60 Hertz
Hoat Treatm~nt (inches) 15,000B 16!000B 17,000B ~lOH
1025C anneal 0.0107 0.547 0.656 0.748 18S6
1175C ann~al 0.0108 0.503 0.600 0.671 1867
EXAMPLE IV
A melt of the following co~position wa~ prepared
a8 describ~d in Exampl~ III:
Silicon 3.25 Per cent
Sulfur 0.008 ~ n
Mangan-~e 0.008 a n
Carbon 0.022 u u
Boron 12 parts per ~illion
Nitrogen 22 ~ ~ ~
Oxygen 37 " u n
The re~ulting magnetic propertie~ after procressing a~ set forth
in Bxample III, xcept that a reheat temperature of 1150~
was used in hot rolling, were:
A.C. Lo~- at 60 Hertz
Heat Thicknesa _,500 q~. 16 300 gs. 17,000 qa
Treatment (inches) (watts/lb) (w;tts/lb)(~5~3
1025C
ann-~l 0.0107 0.508 0.611 0.692 1876
1175
reann-al 0.0108 0.497 0.589 0.658 1882
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EXA~P~ V
A ~lt of th~ following co~position waJ prepared
in accordance with the proceduro ~et forth in ~xa~ple II}~
Silicon 3.3 p-r cent
Sulfur 0. 006 n
M~gi~l~l81~ o. 005 ~ n
c~rbon 0.002 u
Boron 50 parts per million
3 Aluminum 30 n ~ n
~ 10 ~itrogen 24 u n ~
Oxygen 24 ~ ~ n
Iron Re~ainder
~ The resulting ingot was hot and cold rolled and otherwise
:~ procos~ed a~ d~scribed in Example III. The r~sulting sheet
product had magnetic propertie~ after annealing of 5
Thickne8 A.C. Loss at 60 ~ertz
~e~t Treatment (mil~)15,000 gs. 16,300 gs.~lOH
~watt~7Ib) ~watts/lb)
1025anneal 10.71.226 1. 379 1465
1175 reanneal 10.71.149 1.266 1443
EXAMP~E VI
I~ an operation si~ilar to that of Example III wherein
- a minimum opportunity was provided for ~he reduction of boDDn
fro~ the crucible, and no boron addition was made to the melt,
a melt of the following composition wa~ prepared:
Silicon 3~5 per cent
Sulfur 0. 008 n
Manganese 0.002 "
Carbon 0.029 u -
Boron 2 parts per million
Aluminu~ 27 parts per million
: 30 ~itrogen 22 " ~ "
~'xy~en~ 19 u u
Iron Remainder
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An ingot of tho 8ize already d~cribed was poursd and hot and
cold rolled with intermediate heat; treatments a~ de~cribed in
Example I. The r~sulting ll-mil ~trip when prepared as an
Epstein pack and annealed a~ in Exa~ple I d~veloped the following
magnetic prop~rtie~s
Thickne88 A.C. Log~ at 60 Hertz
Heat Treatment (mils) 15,000 g~. 16,300 g~ lOH
1025C anneal 10.7 1.075 1.187 1463
1175C reanneal 10.7 1.143 1.256 1441
EXAMPLE VII
A full-~cale mill heat of 159,000 pounds of silicon-
iron was prepared u~ing metal from a basic oxygen furnace.
The melt wa~ desulfurized (sulfur reduced from 0.020 to 0.007
per cent) a~ it was tapp~d and poured into a ladle containing
2000 pounds of burned li~e and 600 pound~ of fluorospar. Iron
~ulfide wa~ then added to bring the sulfur content from 0.007
to 0.009 per cent, and five pounds of 19 per cent grade
ferroboron were added to the ladlo for purpo~es of the
experiment. Tho analysi~ of the metal in the ladle wa~ then
a~ follows:
Silicon 3.20% Alu~inum 0.00~%
Manganese 0.030X Phosphorus 0.00~%
carbon 0.033% Titanium 0.005~
Nickel O.Q94X ~itrogen 0.0033%
~opp~r 0.24~ Oxygen 0.0052%
Tin 0.021% Sulfur 0.009%
~ Chromium 0.043% Boron 0.0008%
Iron Remainder
In~ots cast from the metal were hot rolled from 2450F
to 90 mils thickness and then pickled, a~ described in Example
I, heat treated for five minute~ at 900C, cold rolled to 0.028
inch thicknes~, heat treated thr2e minute~ at 900C, and cold
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rolled to a final gauge of 0 011 inch Tost ~trip~ w re ~heared
in the rolling direction to form an Ep~tein pack and wer~
decarburized by a three-minute heat treatm-nt in hydrog-n of
700F d~wpoint The strip~ w~re then ~nn~aled by h~ating at
a rat- of 50 & p-r hour in nitrogen fro~ 800C to 950C th-n
at the ~amo rate in dry hydrogen to 1025C After holding
thr~o hour~ at this tomperature thc ~trip~ w ro cooled at 50
per hour in hydrogen to 600 & at which temp~r~ture the annealing
retort Wa8 withdrawn to the cooling ch~b~r The meaRur~d
magnotic propertie~ werOE
~hickne~s A C Los~ at 60 ~ertz
(mil~ 15 000 qaus~ 16 300 gaus~ ~10H
10 4 0 590 0 739 1805
EXAMPLE VIII
In anothor operation similar to that of ~xampl~ III
a melt of the following compo~ition wa~ prepar-ds
Silicon 3 28 p-r cent
~angane~o 0 001
Sulfur 0 005 ~ n
Carbon 0 018 H U
Aluninum 0 004
Boron 0 0007 H n
Nitrogen 0 0019 H
Oxygen 0 0026
Iron Romainder
An ingot wa~ poured and processed through hot and cold
rolling stage~ and ~eat treatmonts a~ describ-d in Example 1
and te~t strips of the resulting ll-mil material w ra u~ed to
provide an Ep~tein pack Thi~ pack wa~ h-ated at 50C per hour
in purified nitrogon to 97 s& where it was held for three hours
and then cooled at the rate of 50C per hour at 600 & whereupon
it wa~ placed in a cooling zone of the furnace until the pack
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r~ach~d roo~ t~mp~r~turo The product prov~d to have good
propertie~ whon teJted ~8 doscriblsd above, pormeability being
1898 gaus~e~ per oorsted (in a 10-oer~ted field)
A ~orie~ of experiment~ was performed for purpo3es
of determining the effects of various boron ~nd nitrogen ratios
on th dev~lopment of ~econdary recrystallization during the
final anneal Thus, a total of 8iX separat~ heat~ were prepared,
all of tho same following basic compositions
Silicon 3 25 per c~nt
Sulfur 0 008 n
carbon 0 025 ~ n
Iron Remainder
To four of the heat~, ferroboron was added to provide
a nominal co~po~ition of 50 part~ per million boron, while the
boron content of th~ other two was nominally established at
50 and 75 p rts por million The nitrogen content ranged in
the~- heat~ from 40 to 145 parts per million
EXANPLE IX
The partial pressure of nitrogen in the furnace was
maintained at 30 ~m, and the metal was poured from the ladle
following the ferroboron addition The resulting ingot wa~
hot and cold rollod and heat treated as described in Example
III Analysis of the cold-rolled strip indicated the boron
content to be 30 ppm and the nitrogen content to be 41 ppm
Magnetic propertie~ of the cold-rolled serip product are set
out in Table A below togethor with those of the following
examples
~XAMPI.E X
Following the procedure of Example IX except that
the nitrogen partial pressur~ in furnace was 60 ~m, a cold-
rolled product was obtained which proved on analysis to contain
- 30 ppm boron and 53 ppm nitrogen
- 15 -
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1~)9,Z7ti~
E~CAMP~ XI
Following th~ procedure of E xampla~ IX and X, but
~till further increa~ing the partial pre~sure of nitrog-n in
the furnace to 100 ~, re~ulted in a cold-rolled product which
was similarly found to contain 32 ppm boron and 78 ppm nitrogen
~XAMPI13 XII
Again, tho procedure of Example IX wa~ followed with
the exception that the partial pressuro of nitrogen in the
furnace was 400 mm The cold-rolled product contained 34 ppm
boron and 145 ppm nitrog~n
EXANP~ XIII
Following th~ ~3xampl- IX procedur-, but maintaining
200 n~ nitrogen partial prel~Jure i~ the furnace and adding
~till mor- ferroboron to the ladl~, resulted in a cold-rolled
product containing S9 ppm boron aDd 68 ppD~ nitrogen
: I~XAMPLE: XIV
A cold-rolled strip p~oduct ~hich contain-d on
~aly~i~ 44 pp~ boron and 93 ppm nitrog-n Wa8 ~ade g-nera~ly
in th- mann r d scribod in Exampl- IX through th~ ~ddition to
th- ladle of ferroboron in amount eguivalent to 50 pp~ boron
and by Dlaintaining the nitrogen partial pr-~ure in the r~olting
furnac~ at 200 ~
TABI~ A
A C. Lo8~
Ex~Pl-Thickn-88 (in L ls~cB171cB lOH
D~OiQ8 1 271 --- 1421
X 0108 6871 014 1689
XI 0107 518676 1894
XIIo0107 9301 255 1551
XIII0107 1 139 -- 1413
XIV0107 53~~12 1842
-- 16 --
. .
RD-7794
1~4~7~j8
Whenev-r in this specification and in the append-d
clai~s reforence i~ mado to a~ount~, r~t-~, p-rcentag~-, or
proportion~, the weight ba~is i8 intendbd unlo~s otherwi~e
expressly 3tatod
As usod her-in and in the appendod claimn, the term
~ingot~ moans ~nd rofers to a body made by ~olidifying by any
casting m-thod a Dolton Jte~l aade by any uitablo ~teel-makinq
~othod, and this includ~ a ~lab-liko ingot obtainod by a
continuous c-sting m~thod
- 1~7 -
1.
