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Патент USA US2109271

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Patented Feb. 22, 1938
Daniel E. Krause, Columbus, Ohio, assignor, by
assignments, to Monsanto Chemical
Company, a corporation of Delawarev
. mesne
No Drawing. Application October, 5, 1936,
Serial No. 104,063
10 Claims. (or. 91-73)
This invention relates to a vitreous enameled as 0.10 to 0.3% manganese to eliminate suscep
product. It furthermore relates to an improved tibility to red-shortness and to lower production ‘
ferrous base alloy suitable for use in the manu
It is general knowledge that enameling iron
facture of vitreous enameled products.
One object of the present invention is the pro- ' a?ords fewer defects and rejectionson enamel- 5
vision of an enameled product having increased ing principally because of its lower carbon con
tent. Its lower strength on the other hand makes
strength at elevated temperatures. Another ob
it. more apt to warp and sag unless supported
ject is the provision of an enameled product pro
viding increased resistance to chipping of the well during enameling. In contrast, the enamel
enamel layer. A further object is the provision ing steels are stronger at room temperatures, 10
of an enameled sheet having increased resistance though not materially stronger at the enameling
to de?ection and warpage both at enameling temperatures, and are more prone to contain de
temperatures and‘ at ordinary temperatures. fects in the enameled surface. Moreover, the
steels pass through an eutectoid transformation
Still another object of this invention is the pro
vision of an improved ferrous base alloy suitable which marks the beginning of the change from 15
for use in the manufacture of vitreous enameled alpha to gamma iron. This transformation, the
objects. Other objects and advantages of my A1 arrest, or the lower critical, occurs in the usual
commercial steels at close to 1340" F. The con
invention will become apparent from the follow
version of alpha to gamma iron involving large.
ing description and claims.
In the art of enameling sheet iron and sheet volume changes is completed at the upper criti- 20
steel the various ground and cover coats are ?red cal or the A: arrest temperature. Commercial
enameling iron, due to its relative freedom from
in continuous or box type furnaces at tempera
tures ranging from a minimum of about 1400" carbon has no A1 arrest. It changes to gamma
F. to a maximum of about 1650° F. The base iron at what is virtually the A1 arrest for pure
26 metal is therefore heated to these temperatures iron. This is at 1670° F., a temperature above 26
at which its strength is comparatively low. that normally used in enameling; hence the
Small articles.either drawn or stamped from gamma transformation may not occur on ?ring '
enameling iron.
sheet may through their design promote sum
The A3 arrest for enameling steels varies from
, cient rigidity to withstand deformation, but mas
30 sive articles such as panelings, refrigerator lin ' 1670° F. for those of low carbon to 1340° F. for 30
ings and shells, table tops, stove parts and other those of eutectoid steel compositions. It is evi
related articles do’ not offer su?icient rigidity dent from this and from the fact that the con
.through design and therefore introduce di?icult ' version begins at above 1340° F. that part or all
4 problems for the enameler in seeking to avoid of the alpha iron will be transformed to gamma
iron on heating and that this gamma iron must 35
35 warpage and sagging. Many of the larger ena
meled articles also act as load bearing members ‘revert to alpha iron on cooling from enameling
in the assembled product. For that reason they temperatures. A marked contraction in volume
occurs during the transformation on heating; an
demand increased strength at normal tempera
equally marked expansion occurs during the
tures. _
The ferrous materials now employed for vitre
ous enameling comprise the. commercial pure
iron, known as enameling iron, and the various
grades of enameling and'ordinary steel. Their
composition limits are about as follows:
vision for supporting the articles against the
above mentioned volume changes can be provided
for and the ?nished articles are subjected to
considerable distortion and warpage.
Enameling Enamellng Ordinary
transformation on cooling with the result that 40
in vitreous enameling of steels no adequate pro
While the resistance to sagging of enameling
iron has improved through the’ development of
enamels of lower maturing temperatures, an im
provement in the resistance of enameling steels
to the warpage and distortion arising from con- 50
traction and expansion during phase changes
01 62-0. 05
cannot be accomplished as readily by the same
0. 024). 05
I have now found that the resistance to warp
Enameling iron may at times contain as much
age and distortion is greatly improved by alloy- 55
mg the enameling sheet with phosphorus. Fur
thermore, I have found that the strength ‘of
enameling sheet at high temperatures is improved
found it advantageous, therefore, to employ
phosphorus wherever high strength andexoellent
enameling qualities in sheet are desired. _
by phosphorus; and therefore its resistance to
sagging is improved. I have also discovered that
phosphorus does not enhance such common de
My invention, therefore, embraces an improved
enameling iron and steel of superior strength at .
room and at elevated temperatures and of su
fects encountered in enameling iron or steel as
perior resistance to sagging, distortion and warp
ing. In accomplishing these improvements I al
loy from 0.10% to 1% phosphorus to the iron and
steel; For ordinary purposes the quantity of
copper heading, blistering, reboiling and ?sh
scaling, nor does it a?’ect the adherence or bond
10 ing qualities of enamels when its ‘content is under
0.40%. I have also discovered that resistance to
phosphorus is below 0.35%. and above 0.10%.
chipping of the-enamel is also augmented through‘
strengthening the base metal.
Where exceptional strength is required in enam
eled ware I may employ more than 0.35% phos
I have employed as much as 1% phosphorus in
As the
adherence or bond of the enamel to the base
phorus and in fact increase the phosphorus to a' -
15 enameling sheet with excellent results.
maximum of 1%.
The general accepted maximum percentage of
phosphorus in vitreous enameling sheet is 0.04%
metal was somewhat less at phosphorus con
tents above 0.40% I have preferred to use phos
yet most sheet-makers prefer to keep it under
phorus contents ranging from-0.1% .to 0.35% in
20 sheet requiring good enamel adherence. The
‘enameling stock- containing more than 0.4%
phosphorus, because of its strength and stiff
For large vitreous enameled parts where -
?atness of the ?nished part is of importance an
extra low-metalloid, open hearth steel graded as.
special vitreous enameling sheet is being used. It
ness, is better suited for flat panels and for ware
retains its'flatness under ?ring better than nor
requiring no severe deep drawing operations as. mal steel and it gives better enameling results.
25 well as for ware in which the 'requirement'for ex
This sheet, which may be classi?ed as enameling -
ceptionally‘ good enamel adherence is unimpor
iron, has a total metalloid content including car
bon, silicon, manganese, sulphur and phosphorus
The strengthening e?ect of phosphorus in steel
at normal testing temperatures has been recog- .
30 ,nized for some time.
Tensile properties of phos
- phorus bearing 22 gauge enameling iron and steel
sheet as set forth in the accompanying table il
lustrate this point. The enameling iron con
Type of
‘mm ‘strength
lbsJsq. in.
0. I)
0. so
57, (I!) k
04, M ,
- 71,500
52 (I!)
55. (I!)
62, 500
0. 70
73. (III
l. 07
0. (KB
' 91, 000
53, M
83, (I!)
42, (XI)
’ 2o
0 17
04, 500
40, 500
0. 31
' 75, (XX)
49, ill)
The sheet was normalized before ‘testing.
-It is evident fromtthe listed properties that
55 phosphorus ‘from the standpoint of strength is as
effective as carbon. In other respects it is more
satisfactory ‘than carbon. ' Carbon, for example,
does not improve the strength at elevated tem-,
peratures to the same extent as phosphorus. It
the A; arrest temperature which
causes more alpha iron to transform during ?ring.
' _ Carbon also increases the number of such defects
sagging and warpage and improving the reten
in 2" ‘
tion of flatness on ?ring, by providing a more suitable base-metal for the more brilliant and 40
Elongation .
an, M
46, (I!)
phorus serves as an important element in enam
42, M
49, too
eling sheet by adding strength, thereby reducing
lbs/sq. in.
0. M8
0. 10
Contrary to these teachings I found that phos 35
enamelingsteel contained 0.12 to 0.13% carbon,
0.08 to 0.10% silicon, 05-06% manganese, and
about 0.04% sulphur, with phosphorus as shown.
other than to prevent sticking on rolling and
argues that it must be kept to a minimum in
tained 0.01 to 0.02% carbon, 0.05 to 0.06% man
The prior art teaches that phosphorus serves
no'useful purpose in the manufacture of sheet
35 ganese, 0.02 to 0.01% silicon, about 0.03% sulphur,
and phosphorus as shown in the table.
not in excess of 0.15% of which less than 0.01%
is phosphorus.
‘more permanent higher melting point enamels,
and by increasing the temperature of the upper
critical point, All theseare accomplished with
out detriment to enameling qualities provided
the phosphorus is below 0.40%.
In steel, phosphorus is particularly advanta
geous from another score since it raises the A's
arrest temperature to a» point where the inver
. sion of alpha to ‘gamma iron becomes _of little
importance insofar as producing much distortion
and warpage in the enameled article. The A;
arrest temperature on heating a steel with 0.15
0.20% carbon and 0.03% phosphorus was 1540‘
This was raised to 1595° F. on increasing the
phosphorus to 0.1%. to 1650° F.’ on increasing
vthe phosphorus to 0.2%‘ and to 1700° F. on in
creasing ’the phosphorus to 0.29%. Thus the
marked rise in temperature of the A: arrest with
an- increase in phosphorus content is apparent;
This rise in the A1 arrest temperature result
.ing from‘ the addition of phosphorus is also of
mark'edimportance in enameling irons contain
as blistering, rebelling and copper heading in_ the . ing
manganese. Each 0.01% manganese reduces '
enameled surface.
. >
Phosphorus,‘ on the other hand, improves the
high temperature tensile properties and raises the
A; arrest temperature of both enameling iron and
steel. In the case of enameling steel 0.2 to 0.3%
orus so eilectively reduces the amount ‘of
alpha iron that is converted during ?ring of- the
enamel as to virtually eliminate the distortion‘
rand'warpage which prevail ‘as aw result of this ~
the A3 arrest temperature about 2.5° P.‘ so that
with 0.1 to 0.3% manganese in enameling iron_
its A; arrest temperature may be from 25° to 75°
F. lower than it is for iron. of low manganese
content. The reduction is su?lcient to bring the
arrest temperature below the maximum enamel
mam“!!! temperature and hence su?lcient' to
promote the alpha-gamma transformation dur
ing the ?ring of refractory enamels. The A: at;
conversion when steel‘ is enameled. Moreover, . rest temperatures for enameling iron containing
phosphorus does not intensify the occurrence of
0.11%, and 0.20% phosphorus were
75 common defects appearing in enameled ware. I 0.004%,
1670‘ F., 1780" It, and 1950' 1"., respectively.-_
' n.
In a previous application, Serial .No. 81,338,
2. A vitreous enameled article comprising a
filed May 22, 1936, I have shown the strength—_ layer of vitreous enamel vitri?ed upon the sur
ening e?‘ect of phosphorus in iron and steel for face of a steel sheet, said steel containing 0.1%
service at elevated temperatures. In‘this respect ‘ to 1.0% of phosphorus, 0.01 to 0.25% carbon, 0.01
5 it is superior to carbon. As aresult of alloying to 0.10%‘ silicon, 0.02 to 0.55% manganese, 0.01
phosphorus to enameling iron and-steel I have to 0.05% sulphur, the remainder being vsubstan-i
found the increase in strength at elevated tem
tially iron.
peratures is re?ected in greater resistance of
3. A vitreous enameled article comprising a - '
sheet to sagging; This was demonstrated by layer of vitreous enamel vitri?ed upon the sur
10 enameling 4" by 10" specimens of 22 gauge sheet face of an iron sheet, said iron sheet containing
which were coated with 9.8 to 11.8 grams of from 0.1 to 1.0% of phosphorus, 0.01 to 0.035% w
ground coat enamel and ?red at 1580" F. for 4 carbon, 0.01 to 0.07% silicon, 0.02 to 0.30% man
minutes. They were supported on the ends leav
ganese, 0.01 to 0.05% sulphur, the remainder be
ing an unsupported span of 3% inches in the cen
15 ter free to sag.- The de?ections after ?ring pro
' vided a measure of the resistance to sagging.
a series of enameling irons containing from
0.005% to 0.40% phosphorus these measured per
manent de?ections were as follows:
20 .
Phosphorus oon-
Permanent de?ection in
tent in percent .
0. 40
ing substantially iron.
4. A vitreous enameled article comprising a 15
layer of vitreous enamel vitri?ed upon the sur
face- of a ‘steel sheet, said steel containing from
0.1 to 0.35% phosphorus, 0.01 to 0.25% carbon,
0.01 to 0.10% silicon, 0.02 to 0.55% manganese,
and 0.01 to 0.05% sulphur, the balance being sub 20
stantially iron.
5. A vitreous enameled article comprising a
layer of vitreous enamel vitri?ed upon the sur
face of an iron sheet, 'said iron containing from
01.02 ,
+0. 02 (arched upward)
0.1 to 0.35% phosphorus, 0.01 to 0.035% carbon, 25
0.01 to 0.07% silicon, 0.02 to 0.30% manganese,
0.01 to 0.05% sulphur, the remainder being sub
The reduction in sagging as shown by these
stantially iron.
30 tests is due to the ‘phosphorus content of the
6. A vitreous enameled article comprising a‘
sheet and to the in?uence of phosphorus on high’ coating of vitreous enamel, vitri?ed upon the 30
temperature strengths of sheet.
surface of a ferrous alloy sheet, said sheet con
An enameling steel such as I prefer to use for taining from 0.1 to 1.0% phosphorus, 0.01% to
the manufacture of enameled sheets may have ‘0.25% carbon, 0.01 to 0.10% silicon; 0.02% to
35 the following composition, where enamel adher
ence is not of major importance:
0.55% manganese and 0.01 to 0.05% sulfur al
loyed therewith, the balance being substantially
Phosphorus___________ __between.._ 0.10 and 1.0
Carbon. _________________ __do_..__ 0.01 and 0.25
Silicon __________ ____ _____ __do____ 0.01 and 0.10
7. A vitreous enameled article comprising a,‘
layer of vitreous enamel vitri?ed upon the sur
face of a steel sheet, said steel containing su?i
Manganese ______________ __do____ 0.02 and 0.55
cient phosphorus alloyed therewith toraise the
Sulphur ____ __.. ____ -;. _____ __do_..__ 0.01 and 0.05
upper critical temperature of said steel above '
Where enamel adherence is of importance I
“ prefer to use between 0.10 and 0.40% of phos
the maturing temperature of said vitreous
8. A vitreous enameled article comprising a
. phorus in a steel which otherwise has an. analysis layer of vitreous enamel vitri?ed upon the sur 45
face of an iron sheet, said iron containing be
as given above.
An enameling' iron suchas I prefer to use for’ tween 0.01% and 0.25% carbon together with the
the manufacture of enameled sheets may have usual alloying elements in iron sheets employed
50 the following composition where enamel adher for enameled articles and containing, in addition,
su?icient phosphorus alloyed with said iron to‘,
ence is not of major importance:
V raise the upper critical temperature of said iron
Phosphorus__________ "between" 0.10 and 1.0
to above the maturing vtemperature of said
___-.. ______ _; ____ __do_-__ 0.01 and 0.035
55 Silicon} _______ __- _______ __do____ 0.01 and 0.07 _
Manga ese ______________ __Ydo____ 0.02v and 0.30,
Sulphur ____ __'_ ______ __‘___do_>___ 0.01 and 0.05
9. A vitreous‘ enameled article‘ comprising a
layer of vitreous enamel vitri?ed upon the sur 65
face of a steel vcontaining between 0.01% and
0.25% carbon together with the usual alloying
elements and impurities in steel sheets employed
Where enamel adherence is of importance I for enameled steels, and containing, in addition,
*0 prefer to use between ‘0.10 and 0.40% of phos- ' sumcient phosphorus alloyed therewith to raise
phorus in an iron‘ which otherwise has an anal
the upper critical temperature of said steel to
ysis as given above.
above the maturing temperature of said enamel.
Having now particularly described my inven
10. A vitreous enameled article possessing an
tion and the manner in which it is to be carried extended plane surface comprising a layer of
35 out, I desire that it not be limited except as indi
vitreous enamel vitri?ed upon the surface of a
' cated by the prior art, or as particularly pointed ferrous alloy in sheet form containing from 0.01
out in the claims.
to 0.25% carbon and containing in addition suf
?cient phosphorus alloyed therewith to retain
1. A vitreous enameled
’0 layer of vitreous enamel vitri?ed upon the sur
face of a'steelesheet said-steel containing from
0.1 to 1.0% of phosphorus, the balance being iron
containing the usual impurities ordinarily oc-v
curring in enameling steel.
said plane surface substantially without sagging
or warping, at temperatures approximating the 70
maturing temperature of the said enamel.
DANIEL n. muss.‘
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