July 25, 1950
P. J. WILTON
2,516,282
APPARATUS FOR I-iEAT-TREATING STEEL
Filed April 27, 1946,
2 Sheets-Sheet 1
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PatentedJuly 25, 1950
21,516,282
UNITED ‘STATES PATENT OFFl/CE
APPARATUS FOR HEAT-TREATING STEEL
Percy J. Wilton, Gary, Ind., assignor to Carnegie
Illinois Steel Corporation, a corporation of New
Jersey
Application April 27, 1946, Serial No. 665,357
2 Claims. (01. 29a_106>
2
The present‘ invention is directed to an ap
paratus for carrying out a process for thermally ,
treating steel which imparts to the metal advan
and rusting induced by the use‘ of aqueous
quenching baths.
The aforementioned obstacles have been met
tageous cold-forming properties, and particularly
in steel plants making alloy'steel sheets through
to an improved method of thermal treatment of
a compromise consisting in the use of normaliz
alloy steels which prevents formation of band
ing and induces additional corollary improve
ments in the mechanical characteristics thereof.
ing\ in place of quenching and drawing, at the
cost of reduced mechanical properties and only
a partial elimination of ‘banding. In this meth
od, strip or sheets were fed’ continuously into a,
Commercial experience has taught the steel
industry several ways for suppressing banding 10 normalizing furnace con?ning a properly Se
lected atmosphere for reducing surface oxidation.
tendencies oi steel. Such procedures usually in
The material introduced was gradually heated
volve bringing all of the constituents of the steel
to the temperature, or slightly below the tem
into a solid solution, and then transforming the
steel into the alpha state by cooling at a rate ‘ perature of the hot zone of the furance, usually ‘
suiliciently rapid for preventing migration of ' 15 ranging between 1700° F. and 1750° F., and then
respective constituents throughout correspond
ing gains. Quenching and tempering may be
allowed to cool in the controlled atmosphere dur
ing the travel through cooler portions of the
furnace to a temperature substantially preventive
mentioned as examples of such procedures.
of surface oxidation of the sheets. Heat treated
Quenching in water and tempering, which is
a satisfactory procedure for preventing band 20 sheets were subjected to a spheroidizing anneal
or used without this treatment, depending upon
ing in steels in many instances, fails to achieve
the requirements of the ultimate application.
the desired results when a ?nal product is sought
Spheroidizing annealing, when used, accentuated
which is to have a maximum softness, particu
the degree of banding resulting from the primary
larly when high ductility requirements are equal
treatment.
ly present. The latter properties are associated
It has been found that the properties of steel
conventionally with the spheroidized structure,
can be improved greatly, particularly in respect
speci?cally when the latter is achieved by straight
to the yield point and handing removal, by in
annealing under the lower critical temperature.
creasing the cooling rate, after heating to the
It has been found that the spheroidizing treat
ment of water-quenched steels has to be con 30 austenitizing temperature, above. the rate re
quired in normalizing, but below the rate induced
ducted at higher temperatures, which tempera
by quenching in liquids.
tures occasionally may convert the original mar
After an extended investigation it has been
tensitic areas into undesirable well-laminated
discovered that the cooling rate induced by the
pearlite in place of spheroidized cementite and
partially restore its banded structure.
35 application of supersaturated vapors, exempli
?ed by wet steam. to sheets heated to austenitiz
The deleterious effect of banding, and of
ing temperature induces a cooling rate that is
changes in the properties of the metal induced
optimum from the standpoint of banding elim
by treatments resorted to for elimination of
ination and mechanical properties produced,
banding, is particularly noticeable in sheets and
similar thin bodies of large dimensions during 40 provided a proper control is exercised in steam
application. Steam-cooled sheets possess a
cold-forming operations to which they are sub
higher yield point, a substantially greater free
jected in the course of the usual manufacturing
dom from banding, and have an unimpaired
processes. There is not known any treatment
surface.
'
industrially suitable for elimination of banding
The‘present invention provides an apparatus
in sheets without undesirably ail’ecting the prop v45
for carrying out the above-outlined procedure in
erties of the metal treated.
an e?ective manner without requiring extensive
Application of treatments found e?‘ective for
modi?cations of existing equipment, and the
banding elimination in bars and similar bodies,
invention relates more speci?cally to a nozzle
such as, for example. quenching followed by a
tempering operation, is not feasible from the 50 or instrumentalities for directing quenching
practical standpoint when applied to sheets, par
?uid, such as steam, upon the shapes being
ticularly during continuous operations. Two ad
treated.
ditional major obstacles have to be considered
- The invention will be understood more readily
in this case, namely, excessive warping, warping
by reference to the accompanying drawings, in
induced by immersion in liquid cooling media,
65 which: >
0
~
2, 5 18,882
3
.
'
-l"igure _1 is a fragmentary longitudinal sec
onal elevation of ?uid injection means embody
ing the improved features of construction of the
ports II; and it is found in practice that theI
general e?‘lciency oi the quenching rests hea
present invention;
Thus, representative photomicrographs of a
specimen of steel which has been subjected to
on the liquid content, of the steam used.
Figure 2 is a rear elevation of the ?uid injec
tion' means of Figure 1, as projected on the plane
of the line 11-11 of Figure 1;
>
‘
normalizing treatment followed by spheroidizing
annealing, and to steam quenching and spheroid
izing annealing, show that, inspite of identical
temperatures in the heating zone of the furnace,
-
Figure 3 is a transverse sectional elevation on '
., the line III-III of Figure 1; and
Figure 4 is a diagrammatic longitudinal sec 10 the same speed of travel, and exactly similar
tional elevation of a furnace embodying the pres
steps during the spheroidizing annealing, the
ent invention.
normalized specimens have a banded structure
outlined by ?ne particles of cementite and incom
'
Referring more particularly to the drawings,
the ?uid-injection means of the present inven
pletely coagulated pearlitic lamellas, while steam
tion comprises a tube A having a closed end B 15 quenched samples are free from any suggestion
and a plurality of nozzles for directing ?uid on
of the former structure, and are characterized
to the heated shapes to be quenched, not shown.
by uniformly distributed particles of cementite
It will be understood that the tube A is adapted
much coarser than those observed in normalized
specimens.
to be inserted in a suitable heat treating furnace,
indicated at C, or exteriorly of the furnace adja 20 This difference in structure of the same steel
cent thereto. The furnace C is shown to be a
resulted in di?erences in physical properties and
conventional type of annealing furnace, having
marked differences in cold forming character
istics during deep drawing. The difference in
conveying instrumentalities D therein, which
furnace has been modi?ed for the purposes of
cold forming characteristics of steels having a
the present invention by removal of a section of
structure associated with a normalizing treat
the cover and introduction of a stack E and
ment as contrasted with steels having a structure
quenching tubes A, constructed in accordance
produced by steam quenching is more marked
than differences in tensile properties, since tensile
. with the present invention.
properties and other physical tests are not the
Each tube A has a Venturi throat adjacent
the open intake end 5 thereof. A ?uid-supply 30 only true criteria for comparison of steels which
pipe 9 enters said end and is secured therein by
exhibit poor deep drawing characteristics with
radial ribs ‘I welded in place. A source of quench
steels having good deep drawing characteristics.
Di?erences in microstructure resulting from nor
ing ?uid (not shown), e. g., steam, is connected
to pipe 9 and ?uid entering the tube A induces
malizing and from steam quenching have been
atmospheric air through the intake ports [5 in
found to be very de?nite guides in predicting
success or failure in deep drawing. This dif
the end 5 thereof. A sliding valve H, mounted
on the intake pipe 9 and provided with an end
ierence, namely, the degree of banding present,
?ange l3 positioned towards the end 5 of the
often can be used as a criterion of formability
Venturi tube A, is controlled as to its position
when other steel characteristics are approxi
relative to the end 5 by. means of a set screw 40 mately similar.
it which engages the intake pipe 9 and may be
There is established de?nitely a pronounced
tightened thereagainst for holding the valve II
improvement in sheets as a structural material
in proper adjusted position. The ?ange [3 on
for cold forming applications by interposing the
the valve H has a diameter su?icient to close
supersaturated vapor quenching step under prop
the air intake ports I5 when the valve I l is moved 45 erly regulated conditions in the series of process
against the intake end 5 of tube A; and the
ing operations used in heat treating the shapes;
amount of air admitted through the ports [5 is
and it is found in practice that suitable regulation
controlled by the distance the ?ange i3 is posi
tioned from the intake end 5 of the tube A.
The tube A has a plurality of holes i'l provided
of steam temperature, its water content, and
method of application to ?t modi?cations in com
position and gauge of the shapes, make steam
with nozzles IQ for directing quenching ?uid
quenching and the bene?cial e?ects derived
against the shapes being quenched. For guiding
therefrom applicable to both carbon and alloy
the resulting jets of quenching ?uid, de?ector
steels.
plates 2| are provided, which conveniently are
It has been stated above that the general elli
welded to the pipe A and to nozzles l9, and serve 55 ciency of the present invention rests heavily on
to direct and to concentrate the quenching ?uid
the liquid content of the steam used, since it has
onto the heated shapes being quenched.
been demonstrated that dry steam does not exert
When steel shapes such as a strip, sheets, or
a cooling e?ect su?iciently rapid for producing
other shapes, heated to a temperature above
the desired results. The degree of saturation
the Ara critical point, pass under the quenching 60 which is important from the standpoint of the
tubes of this invention, they are quenched by
present invention is the saturation in contact
suitable number of jets of the ?uid issuing
with the articles being quenched and independent
through the parallel nozzles i9, and impinging
of the properties of vapors in supply lines. On
on the shapes at an angle‘of substantially sixty
. this account, a close attention must be paid to the
degrees to the surface of’the shapes as shown in 65 pressure selected, the size of ori?ces delivering
Figure 4. The holes I1 may have in practice a
the vapors, the distance of the ori?ces from the
to
diameter of substantially 1A; inch, for example,
quenched Objects, the angle of vapor impact '
and where the quenching medium is water-bear
thereon, and the surrounding atmospheric con
ing steam, it may be fed through the intake pipe
ditions. An application of the wet steam to one
9 under seventy-?ve pounds pressure, for ex 70 side of the shapes being quenched frequently is
ample.
adequate for achieving the desired results, but in
It will be apparent that where steam is the a
quenching medium applied to the shapes, it will
be mixed with water due to partial condensation
of the steam by air drawn into it through the 75
some instances, particularly with heavier sheets,
better quenching is attained by applying the
steam from both sides of the shapes. ‘
, In Figure 4 of the drawings, the stack E is
2,516,282
shown as extending transversely of the heating
‘chamber of the furnace to lead hot gases out of
the furnace while permitting passage of the
shapes through it.’ This stack structure forms no
part of the present invention but is more fully de
scribed and claimed in Patent No. 2,466,870 issued
on an application ?led by Arthur E. Twiehaus and
me. The tubes A are joined by straps 23 each-of
which has an opening or eye 25 which are in reg
istry to permit insertion of the suspension rod 2'!
by which the tubes A are removably suspended in
the furnace. The stack and quenching tube as
semblies may be removed entirely from the fur
nace, which upon replacement ‘of the removed
said tube having laterally directed nozzles spaced
therealong and a Venturi throat at one end, the
other end being closed, an elongated de?ector
plate extending along said tube, one edge of said
plate being disposed tangential to the tube and
the other edge of said plate projecting into the
line of discharge from said nozzles, and a ?uid
supply pipe smaller than said one end of said tube
extending thereinto, leaving an annular air inlet
between the pipe and said tube.
in the furnace chamber including hangers spaced
I along the tube.
cover, is directly restorable to conventional opera- ‘
tion. ‘From the drawings, it will be seen that the
tubes A are mounted in the furnace by suspension
from the bar or rod 21, the ends of which are re
ceived in the side structure of the furnace, as
indicated at 29.
_
While certain speci?c embodiments of the pres
entinvention have been described and illustrated
as examples or one form of apparatus that is
suitable for carrying out the invention, it will be
understood that the construction'of the spray .
pipe of the present invention is not limited rigidly
to the speci?c details of the structure thathave
been herein illustrated and described; and it will
be understood that it 'is intended and desired to
embrace within the scope of this invention such
modi?cations and changes as may be necessary to
adapt it to varying conditions and uses, as set‘
forth in the appended claims.
I claim:
,
'
1. A quenching tube adapted to be mounted
transversely of _an elongated furnace chamber, 35
'
2. The apparatus de?ned by claim 1 character
ized by means for removably mounting the tube
'
PERCY J. WILTON.
REFERENCES CITED
The following‘ references are of record in the
?le of this patent:
Number
'
UNITED STATES PATENTS’
Name
Date’
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1,914,934
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Jackman et al. ____ .. Jan. 7, 1919
Snow et a1. _______ __ June 9, 1931
Miller ____________ _- Aug. 18, 1931
Adams et a1 ________ __ Oct. 6, 1931
Shanafelt et a1 .... __ May 24, 1932 .
Talley ___________ __ Nov. 22,1932
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Leser _..__' ________ __ Nov. 21, 1933
Marcy ___________ __ June 15, 1937
2,352,709
,
Haase ____________ __ July 4, 1944
Certi?cate of Correction
Patent N 0. 2,516,282
'
July 25, 1950
PERCY J. WILTON
It is hereby certi?ed that error appears in the printed speci?cation of the above
numbered patent requiring correction as follows:
Column 1, line 17, for the Word “gains” read grains;
and that the said Letters Patent should be read as corrected above, so that the same
may conform to the record of the case in the Patent O?ice. '
Signed and sealed this 7th day of November, A. D. 1950.
[am]
THOMAS F. MURPHY,
Assistant C’ommz'ssz'oner of Patents.