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THESIS

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MAURICE G, JEWETT © CLIFFORD R. WIGGINS

1920
THESIS
 

 

 

 
A STUDY OF THE GROTH OF A O20 CARBON
CHROM NICKEL STEEL RING GEAR

UPON HHEAT-TREATHONT

& THESIS
Submitted to the Faculty of the

MICHIGAN AGRICULTURAL COLLEGE

By
+ jek . Ws se
Maurice G. Jewett Clifford R. Wiggins

Candidates for the Degree of
Bachelor of Soiense.

June, 1920.
va ESAS

>
TABLE OF CONTENTS

—_

Introduetion -- -------.----..-.

Chapter I ---+--+---+-+-+-+-+--+-+-+--
fhe Scope of the Thesis.

Chapter II -- -----+--+--+-+------
Fheoretical Considerations

Chapter III ----+-+-+-+-+-+-+-+-+-+-+-
Metallographical Examinations.

Chapter IV -------+--+-+-+-+-+-+--.

Pests and Results.

Ohapter V -- -- ------+------e--

Conelusiens.

100244

Page

Lz

L5
INTRODUCTION

For several centuries it has been a matter of
common knowledge that metals expand upon heating and
contract upon cooling. However the law which
econtrols the amount of expansion or contraction
which occurs above the lower critical point has not
been determined. It has not been known until the
last few years, that at least ferrous metals have a
range of temperature where the addition of heat does
not cause an expansion, but does cause a contraction.
The exact location of this temperature range varies
with the chemical analysis of the metal. No two
authors however report the same figures on similar
metals for this range. This subject is at present
being investigated by many metallurgists, since the
determination of some law, ooncerning the expansion md
contraction of metals during the oritiocal range, will
solve many problems now confronting the industrial

world.

suoh a problem has for some time confronted
the Reo Motor Car Company, of Lansing, Michigan, and
although it has not been so serious as to prevent
production, still it has been a problem that disturbed
the @gineering department.
In the first capter, the authors have
endeavored to give complete information ooncerning
the problem confronting the Reo Motor Car Company,
as well as the routine method of manufacturing their
ring-gear, Which is the part on which this thesis is
written. In the seoond chapter is given an explanation
ef the theory upon which the actual tests in chapter
‘four were based. Chapter three gives the results of
a metallographical examination of the ring-gear.

This work was merely a preliminary examination,
carried out before the actual tests on the theory
involved were begun. Chapter four is a compilation
ef the data and results of the actual tests run.
Chapter five gives the conolusions which were arrived

at from a careful study of this data.
Chapter 1.

THE SCOPE OF THE THKSIS.

Por some time the keo Motor Car Oompany,
of Lansing, Michigan, has been having trouble of a
more or less serious nature with their ring gears.
During the heat treating process the diameter of the
gear has bem growing larger. The ring gears and
pinions are spiral bevel gears and it is necessary
that the pitch lines of the two gears interseot at
a point in order to have a quiet running gear. When
the ring grows in diameter, the pitch airole is
forced outward and the twe piteh lines no longer
intersect. This causes the gear to be neisy and also
causes trouble in the assembling ef the gear and
pinion.

In order to present the problem mre in
detail, let us take up the chemical analysis and
method of manufacture of the gear. The xeo ring
gear is made from steel of the following chemical

analysis;
Carbon - - - - - - 015 to 25%
Silicon - - - - = LZ
Menganese- - - - - 50 to .80

Phosphorous- - - - .O4 max.
Sulphur - - - - - -04 max.
Niokel- - - - =< - 1.25 to 1.50
Chromium - - - - .80 to .650

The Reo Company receives the gear blanks
after they have been forged. They are inspected
when received and are then placed in storage until
they are needed for production. From the stook
room they are taken te the lathes where thg@ are
machined all over to approximately the sise of the
finished gear,- allowances only being made in places
requiring grinding. The teeth are then roughly out
to shape and immdiately after this a finishing out
is given the teeth on the Gleason Spiral Bevel Gear
Generator. ‘The eight holes are then drilled in a
multiple spindle drill presse md each hole is
countersunk. <After this the gears are taken to the
heat treating department, packed in cast iron
earburising boxes, and carburised at a temperature
ef from 1700 to 1725 degrees Fahrenheit for a period
of frem eight to nine hours. The web and a small
portion of the back is prevented from oarburising
by packing it tightly with fire olay. The boxes are
taken from the furnace and cooled in air. fhe gears:
are then removed from the boxes, brushed to remove

all clinging carburising material, md taken to the
lead pots for the hardening operation. The gears
are heated in the lead pot to a temperature of

1550 degrees Fahrenheit and quenched in 011 in the
Gleason Machine. hey are then heated to 1425 de-
grees in a second lead pot and again quenched in
oil in the Gleason Machine. The gear is removed
from the mechine while quite warm so as to give

the equivalent of a 300 degree drawing operation.
The time required for heating in the lead pet is
about eight minutes. The desired soleroscope hard-
ness of the teeth is from 80 to 90. During the heat
treatment the gears warp, even with the use of the
Gleason Machine, and, consequently, the next operation
is a straightening one. They are then ground to the
correct diameter on the inner hole and ground flat
on the back after whic the gear is run in with a
pinion until the two work together smoothly. The

Bame gear and pinion are then assembled on the car.

It is during the carburising snd the heat
treatment that the trouble which we are investigating
arises. During these processes, the inside diameter
of the gear inereases from five to twenty thousandths
of an inch. If the diameter of the hole grows, the
diameter of the pitch circle will ales grow, and the
gear and its pinion will no longer mesh as designed.
Some of this growth May be taken care of during assemly
by means of the pinion adjustment. As has been stated
before the growth of the gears does not prevent pro-
duction but it does hinder the preduotion of a

perfect product, which is the aim of the mmufacturers.

fhis thoroughly covers the proposition which
the authors were called upon to investigate. ‘The
problem was taken up with the end in view of
determining the cause for the growth of the gears, of
finding a means of preventing this growth, and of
adapting that means to cemmeroial or production
requirement s.
Chapter II.

THEOReTICAL CONSIDERATIONS.

It is almost impossible to find any reliable
information concerning the expansion or contraction
of iron or steel due to heating, no matter where
one may look. And what information one does find
is directly oontradicted by some other author of
eyual standing as a metallurgist.

albert Sauveur, Professor of metallurgy md
metallography in Harvard University and the
Massachusetts Institute of reohnology, in his book
"“Bhe Metallography and Heat-Treatment of Iron and
Steel", throws some light on the subjeot. In
chapter nine of his book where he is discussing the
allotropic transformations in Alpha Beta and Gamma
Iron, he makes the following statement:

“The absence of dilatation as iron oools
through the Arg point, reported by some
(Charpy and Grenet, and Benedioks) has
been claimed to preolude the existence
of allotropy. Some investigators, mre-
over, believe to have deteoted a dilatation
at the arg point while even the results of
 

Benedict's eareful experiments do not
eonclusively prove the absence of

dilatation.*

This leads one to believe that there is a
possibility of there being a period in the cri tical
temperature range, where iron or steel contracts
instead of expands upon heating. fo quote further

from Sauveur:

"As the metal cools past the point Ar,
the following adrupt changes in some of
its properties have been noted. The metal
which above the point ar, was contracting,
as is the general rule with all cooling
bodies, on passing through the point ats
undergoes suddely a marked dilatation,
amunting to over one one-thousandth of
its length, immdiately followed again by
a normal contraction.

On Heating at the Aog point a spontaneous
contraction ecours of the same magnitude as
the dilatation on oooling.

Accomiing to Le Ohatelier, to Charpy and
Grenet, to Jenedick's and others, no dilata-
tion takes place as the metal cools past the
point arp and they see in this an indication
that the ATs is not an allotropic point.
Osmond's reply is that the curves obtained
by Gharpy and Grenet, for instance do

indi cate a dilatation at Arts which, however,
the authors fail to notice because the
transformation not being sudden, the
€ilatation likewise is gradual, whereas

the anthors were looking for sudden dilata-
tions only."

Prom the above quotations it ean be seen that
the fact is generally conceded that somewhere in this
oritiocal temperature range, a contraction takes place
upon heating, but the extent of that range is very
ai ffi cult,

Having, therefore, no dsfinite theory upon
which to base their experimental work, the authors
first had to establish a hypothesis from whic to work.
It was known to the authors, that certain manufacturing
concerns who had experimental laboratories of their own,
had found a solution to this problem. And it was quite
generally oonceded that this solution was effected by
the rate of heating the mtal under test. From this
knowledge, and f.om the information gathered By reading
from all available sources, the following hypothesis
was eatablished.
10

If a metal of known chemical malysis is
heated in a furnace at a constant rate, that is, at
a definite number of degrees per minute, during the
time that the metal is rising from room temperature
to the lower critical temperature point, that mtal is
expanding; while the temperature is rising from the
lower critical temperature point to the upper critical
temperature point, the metal is undergoing a state of
contraction. After passing through the upper
critical temperature point the metal again expamds
and when the piece is finally taken from the furnace
and quenched, contraction takes place. In order to
make the matter clearer, refer to the graphical
illustration on plate number one. During the period
that the metal is heating from the point A to the
point B, which is the lower oritical temperature
point for the particular analysis of steel under
question, the piece expands. While the steel is
passing through the critical temperature range, or
passing from the point B to the point C, the rise in
temperature is not so great per unit of time and this
period is one of contraction. From the point 0 to
the point D another expansion takes place, md a
sudden quench at the point ) causes another contraction.
If the hypothesis is oorreot, than it is only a
patter of making the total expansion equal the total
1

contraction and the piece will be the same size
after heat-treatment as it was before. In order

te make these equal, and from a careful study of
the data obtained from the first three tests te
authors assumed another hypothesis, vis,- that the
greater the rate of heating in a sone of expansion,
the greater will be the expansion, and in a sene of
contraction, the greater will be the contraction.
Or in other words, if a metal was heated from room
temperature to the lower critical temperature in
twenty minutes, it would expand more during that
period than if thirty minutes were taken. Also

if? it took ten minutes to pass through the ori tical
temperature range, the piece would contract more than

if it had taken twenty minutes.

It was with this hypothesis in mind that
the actual experimental work was started, the results
of whioh are given in the next chapter.
12

Chapter III.
METALLOGRAPHICAL EXAMINATIONS.

The work in this ehapter was carried out
not with the aim of obtaining definite ideas re-
garding the subjeot of this thesis, but rather to
supplement and enlarge the authors’ own knowledge
of the microstructure of steel. <All samples of
steel after polishing were etohed with a ten per-
cent solution of nitric acid. The photographs
show a magnigication of eighty diameters.

Figure 1, shows a photomiorograph ef a
sample of the steel as it was received from the
machine shop ready for the carburising operation.
fhe structure is typical of nickel steel as evidenced
by the sharpness and angularity of the pearlitic
particles end by the smallness of the ferrite crustals.

After the carburising operation a photomi-
crograph was taken of a sample of the core and this
is shown in Figure 2. The most noticeable fact about
this sample is the laminations of the ferrite and of
the pearlite. This 1s an undesirable characteristic
of nickel steels as it has the tendenoy to weaken them
unless the steel is properly refined.
13

& photograph was also taken of the case
after the carburisetion and is show in Figure 3.
Although the specifications oalled for a case of
three hundredths of an inch in depth, in reality
it was slightly over one sixteamth of an inoh.
fhere is a dlight excess of cementite in the case

but probably not qmough to de any harn.

In our next photograph shown in Figure 4,
we have a sample of the core after the hardening.
It is m exceptionally fine structure and very tough.
The laminations which appeared after carburising
have entirdly disappeared. ‘fhe case of this sample
was practically all martensite and a photograhh
would have been of little value. The authors had
great diffimity in seouring the sample for this
picture. ‘fhe gear was first broken into several
pieces in the Riehle Testing Machine. Difficalty
was enoountered, however, in the breaking off of a
single tooth for a sample. it could neither be broken
by the blows of a hammer nor by those of a sledge be-
cause of the toughness of the core. As a last resort,
a round bar of steel was wedged between two of the
teeth being driven down with a heavy sledge. By this
means a small portion of a tooth was broken off.

A sample ef the steel was then normalised by
14

holding it at a temperature of 1800 degrees for about
three hours and slowly cooling it in the furnace,-
the entire time required being about thirty six hours.
Figure 5 shows a section of the core after it had re-
ceived this treatment. Here the laminations are even
more pronounced than those ocouring in the oore after
carburisation. The case of this sample was moh the
same in appearance as that of the carburised sanple
shom in Figure 3.

Yinally, one of the normalised samples and
one of the hardened samples were kept immersed in a
ten percent solution of hydrochloric aoid for twenty
hours. This was to determine the presence of strain
lines which, if present, would onause sharp ridges to
be etched in the steel. It wuld be possible to see
these with the naked eye. However, none of these
ridges appeared, which proved that these strains

were absent from the piece.
15

Ohapter IV.

TESTS AND RESULES.

From the test data of experimats run by
the company previous to our undertaking the work
1% was found that the gears as a rule grew during
carburising as well as during the heat-treatment.
However, the growth during the carburising process
was small in comparison with the growth during the
two heat-treatments. The data in table number one
was taken from the experina@mts run by the company amd
condensed. fhe first twelve gears were taken from
stock, and the first heat was quenched in a tank,
the second heat being queched in a Gleason Machine;
gears number thirteen to eighteen inolusive were
annealed at 1475 degrees fahrenheit before treatment
and numbers nineteen to twenty four were again taken
from stock. Sinoe we desired to acoompliah results
that could be adapted to an oil buming furnace, we
@ecided to do our experimental wrk at the keo factory
eas far as was possible. In order to get m even heat
we placed three gears in a cast iron carturising box
and packed them with ocarburising mterial to prevent
oxidation. These gears had beem earefully measured
across the inside diameter, in two places at right

angles to each other, and the measurements recorded.
16

Numbers were stamped at the points on the circumference
where the gears were measured so that all following
measurements would be at the same points. fhe box

Was placed in the furnace and heated at the rate as
shown by the data for the first heat in table

number two. As there was no pyrometer in the box
itself, these temperature readings may not correspond
to the temperature of the gear. After they were up

to heat, the gears were quenched in the Gleazon
Machine.

realising that we should get the temperature
of the gears more accurately, on the second heat we
Placed only a little carburizing mterial in the
bottom of the box containing the gears mé sealed
the cover on with fire alay. The thermocouple of
a pyrometer was placed in the box through a hole
dn the side and about two thirds of the way towards
the top. This pyrometer registered the temperatre
of the gears in the box while another pyrometer
gave the temperature of the furnace. The data for the
second heat of the gears numbered one to three

inclusive is also given in table number two.

Phe test on these first three gears gave us
gome idea of the difficulties to be encountered and,

now that we had overcome most of these, we ran
—_—
17

another test with gears number four, five and six ©
at the same rate of heating and discarded the re-
aults obtained at first because of their inacauracy.
This rate of heating was as fast as was possible
for us to obtain with an o11 burning furnace. The
results of this test are given in table number
three.

bince it was the general tendenoy for the latter
gears to grow, the next test was made by using a slower
rate of heating. that we might establiah the limits
within whioh it was necessary to work, we made this
the slowest rate at which it wes practical to
operate the furnace. also since there had been a
tendenoy for the gears to warp, four masurements of
the diameter were taken, one on the extreme front edge
of the web, (indicated by the letter "a" on the blue
print of the gear); one on the extreme beek edge
(indicated by the letter "B* on the blne print ef the
gear) and the others at right angles te the first two.
The results are shown in table number four. The
curves directly following the data tables, show
graphieally the rates of heating for each heat.

fhere was a large variation in these results
but still there was a growth. Since we could not heat
alower in the o11 fumace, and in order that we might
control the rate of heating better, we decided to use
x
18

the electric furnace in the college laboratory.
However, it was impossible to place a whole gear in
this furnace, due to its sise. we ooneluded that

if the gear grew in diameter, a segment of the gear
would grow in length, so that for the tests in the
electric furnace, segments about five inches long
were used. ‘The ends of the segments were milled so
that they would be parallel and a true surface about
one half inch square was carefully soraped from which
to take all the measurements. The average of six or
eight readings taken on this small surface, was taken
as the true reading. If we oould prevent the segment
from growing in lagth, we assumed that the gear would
not grow in diameter under similar heat-treatment.
fhe data in tables number five, six and seven are

the results of tests run in the electric furnace.

There was very little change of length in
tests number five and seven end it was concluded that
this was the rate of heating that we desired. Now to
test this rate of heating on a whole gear, we used a
gas fired furnace in the college heat treating
laboratory and adjusted the burner so that the
temperature as nearly as possible would follow the
curve of tests number five and seven. ‘he results of

these tests are given in tables eight and nine.
iP

48 can be seen, these results were far from
what we exvected. ‘the rate of heating varied but
very little from the rate of heating in tests number
four and six but still the gears grew. As a last
means of determining the effect of the rate of
heating, we heated a gear in the gas fired furnace as
Slowly as was possible until the temperature of the
lower critical point had been reached, then the rate
was rapidly increased until the gear was qumohed.
Acoording to the hypothesis on which we had been
working this should have oaused a decided shrink but
instead a decided growth ooourred.
TABLE WUMBEH I.

Data showing growth during oarburising and heat-treatmnt.
(Reo experimental results condensed)

AV. AY.

 

No. Diam Liam dure) obaem. 6 dure G@rooth
mi. “ier CBF oy GRE
ising heat. heat. heat. heat. izing.
1 6.9625 6.9965 .914 6.9980 .0015 0155
2 6.9805 7.0002 .0197 6.9995 -.0007 .0204
3 609835 6.999 .0155 6.9937 -.0053 .0102
4 6.9802 =«-«4& 9907-60105 «6.9932 0028 018
5 6.9835 6.9807 -.0028 6.9837 .003 0008
6 6.9825 ° 6.9822 -.0003 6.9822 .000 -.0008
7 6.9822 7.0037 .0215 7.0036 .0003 .0218
8 6.9805 7.991 .0205 7.0015 .0105 .021
9 6.9802 6.9947 .0145 6.9907 -.004 .0105
10 6.9765 6.9917 .0152 6.9895 -.0022 013
11 6.9787 6.9985 .0198 6.9967 -.0018 .0180
12 6.9837 6.9695 -.0142 6.9882 .0187 .0045
13 609855 6.9992 .0137 7.001 .0016 .0155
14 6.9832 6.9862 .003 6.9862 .000 008
15 6.9882 6.9876 .0053 6.987 -.0005 .0048
16 6.9637 6.9865 .0028 6.9825 -.004 0012
17 -—«s«6. 9865 «=««6 .985-—s«~=.0015 6.981 -.004 -.0055
18 6.985 6.987 .002 6.9872 .0002 0082
RL

TABLE NUMBER I (Cont'd)

 

AV. AVe Growth AV Growth Total
No. Dian. Diam. aur- Diam. aur- Growth
of after after ing after ing after
Gear Oarbur- ist is 2nd 2nd Carbur-
ising heat. heat. heat. heat. ising.
19 6.9842 6.9892 .005 6.986 ~.0032 -,0018
20 6.9817 6.987 e0053 6.982 e005 00103
22 6.982 6.9885 0066 6.985 -.0035 2003
23 6.9855 6.9835 -.008 6.986 0025 e005
NOTE: The sign - indicates a shrink instead of a growth.
Test results for gears numbers one, two and three.

TABLE NUMBER II

Growth

28

 

AV. AY. Growth AV. Fotal
Wo. Diam. Diam. dur- Diam. dur- Growth ©
of after after ing after ing after
Gear Carbur- let ist 2nd 2n Carbure '
ising heat. heat. heat. heat. ising.
1 6.9852 6.987  .0018 6.991 .004 0088
2 6.9865 6. 9845 -.Q002 6. 983 #0015 #00385
$ 6. 980 6.987 ~007 6e 985 #-.Q08 e008
1550 begree 1425 Degree
° heat heat
Time Femp. hand emp. office Time emp. Temp.
pyrometer pyrometer Furnace Box
1:20 1200 1210 8: 52 1195 435
1:3 1276 3;55 1300 650
1:40 1335 1280 9:00 1450 940
1:61 1575 9:05 1426 1045
2:00 1420 9:10 1425 1140
2:10 1470 9:15 1390 1165
2:39 1465 9:19 1410 1200
2:57 1550 9:36 1410 1300
4:28 15765 10; 30 quench
Test results for gears four, five and six.

TABLE NUMBER III

£3

 

AV AV. AV. Growth fotal
No. Diam. Dian. Dian. dur - Growth
of after after after ing after
Gear Oarbur- ist 2nd 2nd Carbur-
i sing heat. heat. heat. heat. i sing.
4 6.9805 6.9842 00087 6.987 e0028 0066
6.987 6.99387 0067 6.9948 0005 20072
6 6.98287 6.990 eOO7% 6.991 e001 -0083
1550 Degree Heat
Time Pemperature
yurnaae pox
103 53 1265 635
(Continued )
10; 55 1295 725
Pemperature
11:00 13965 990 [i me Furnace Box
11:05 1490 1150 11:45 1605 1550
11:07 1520 1200 11:47 1605 1580
11:10 1855 1280 12:01 1590 1555
11.115 1570 1315
11:15 1576 1365
11; 20 1585 1420
11:25 1590 1455
11; 30 1600 1485
11:35 1605 1505
11:40 1605 1525
TABLE NUMBER III (Cont'd)

1425 Degree Heat

2:20

1460

fine Temperature
Furnace Box
1:00 1200 500
1:05 1285 690
1:10 1420 985
1:15 1475 1160
1:20 1470 1225
1:25 1475 1265
1:8 1475 1315
1:35 1470 1340
1:40 1455 1360
1:45 1475 1385
1: 50 1475 1400
1:55 1475 1410
2:00 1475 1415
2:05 1475 1425

1425
TaSLE NUMBER IV

25

Test results for gears number seven, eight and nine.

 

AVe AVe Growth AVe Growth Tot al
HO. Diam. Dian. dure Diam. dur - Growth
of after after ing after ing after
Gear Carbur- lat let 2nd 2nd Carbur-
ising heat. heat. heat. heat. ising.
7 6.981 6.9889 00079 6.9945 0056 0135
8 6.9824 6.986 ~0036 6.984 #002 0016
9 6.9838 6.9894 e0056 6.9906 .0012 e0068
1550 Degree Heat
Temperature
Time Box Purnace
9:19 535 1150
9:24 790 1255 (Cont inued )
9:29 965 1335 1550 Degree Heat
9:34 1060 1385 Time Temperature
Box Furnace
9:39 1090 1430
10:29 1520 1610
9:44 1175 1475
10:34 1540 1620
9:49 1255 1515
10:39 1550 1630
9:54 1300 1550
10:44 1555 1615
9:59 1356 1580
10:49 1555 1695
10:04 1400 1600
10: 54 1560 1580
10:09 1435 1616
10:14 1460 1625
10:19 1480, 1615
10:24 18500 1610
YABLE NUMBER IV (cont'd)

1425 Degree Heat

Temperature
BOX Furnace
510 1200
700 1240
835 1290

960 1360
1065 1415
1160 1475
1210 1480
1270 1490
~510 1510
1350 1495
1375 1490
1395 1500
1405 1500
1420 1500
1425 1490
14H 1475
1425 1460
1425 quench
TABLE NUMBER V

Test results for piece number thirteen.

 

 

Length Length Length Growth

before after ing after during Total

ist heat ist heat ist heat 2nd heat 2nd heat Growth

4.77755 4.7827 4.7776 -.00561 00025
1550 Degree Heat 1425 Degree Heat

Time Femperature Time Temperature

2:45 Current turned on 8:41 Current turned on

2:50 200 8:46 205

2:55 440 8: 450

5:00 670 8; 56 680

5:05 840 9:01 850

$:10 966 9;06 1000

3:15 1075 9:11 1120

$: 20 1175 9:16 1240

5: 26 1265 9:20 1340

3: 30 1350 9; 24 1400

5:35 1425 9:26 1410

8:40 1480 9: 3 1380

5:45 1545 9; 36 1405

3:50 1640 9:4) 1425

5:55 1545

4;00 . 1560

4:05 1545

27
28

TABLE HUMBER VI

fest results for piece number fourteen.

 

Length Length Growth Length Growth

before after dur ing after during Total

ist heat ist heat jst heat 2nd heat 2nd heat Growth
4.9312 4.9320 ~0008 4.9288 -.0082 -.0024

1550 Degree Heat 1425 Degree Heat

Time Temperature Time Temp. Time Temp.
12:25 Current turned on 1:20 Start 3:00 1260
12:30 325 1:25 120 3:05 1280
12:35 340 1:30 240 $:10 1305
12:40 430 Time Temp. 1:35 320 6:15 13365
12:45 530 2:05 1305 1:40 410 3:20 1360
12: 50 620 2:10 1340 1:45 480 5:25 1385
12:55 690 2:15 1370 1:50 6650 $:30 1415
1:00 760 2: £0 1390 1:55 620 3:35 1430
1:05 625 2:26 1415 £;:00 690 3:40 1425
1:10 875 2:30 1440 2:06 765 3:45 1425
1:15 925 2:35 1475 2:10 820

1:20 970 2:40 1490 2:15 875

1:25 1015 2:45 1510 2:20 920

1:30 1060 2: 60 1530 2:26 980

1:35 1095 2:55 159 8:30 1035

1:40 1135 3;00 1560 2:35 1070

1:45 1155 3:05 1576 8:40 1110

1:60 1196 $311 1550 2:45 1150

1:55 1240 2:50 1190

2:00 1276 2:55 1220
Peet results for piece number 15.

TABLE NUMBER VII

 

Length Length Growth

before after ng during Total
ist heat lst heat lst heat 2nd heat 2nd heat Growth
5.03756 §.0785 #-.0038 #0001

Tine
8; 25
8:30
8:35
8:40
8:45
8: 50
6:55
9:00

1550 Degree Heat
Temperature

Started

170
395
635
800
940
1050
1165
1260
1335
1405
1455
1530
1543
1555
1555

1425 Degree Heat

Time
12; 00
12:05
12:10
12:15
12:20
12:25
12:30
12:35
12:40
12:45
12: 560
12: 55

1:00

start
?
520
645
850
1015
1135
1255
1540
1420
1425
1425
1425

29

femperature
v
TABLE NUMBER VIII

Test reeults for Gear number ten.

 

AY. AVe Growth AVe Growth fotal
Yo. Dian. Diam. dur- Diam. dur~ Growth
ef after after ing after ing after
Gear Oarbur- Let is end 2nd Carbur-

ising heat. heat. heat. heat. ising.
10 6.9832 6.9944 eO1l1l2 6.996 .0016 e0128

1550 Degree Heat 1425 Degree Heat

Time femperature Time Temperature
9:11 Start 8:38 Start
9:16 180 6:43 315
9:81 400 8:48 565
9:26 642 9:53 745
9:3) 855 8:58 922
9:36 1000 9:03 1000
(9:41 1085 9:08 1115
9:46 1140 9:18 1250
9:51 1850 9:18 1320
9:58 1370 9:25 1408
10:01 1455 9:28 1425
10:06 1530 9: 53 1426
10:22 1542 Quen ched
10;16 1548
10:21 1552

Quenched
PaBLE NUMBEX Ix
fest results for Gear number eleven.

AVe AVe Growth Av. Growth Tetal
No. Dian. Dian. dur- Diam. dur- Growth
of after after ing after ing after
Gear Carbur- ist is knd 2nd Carbur-

ising heat. heat. heat. heat. ising.
al 6.9874 6.9955 .0081 6.9946 -.0009 e0072

1550 Degree Heat 1425 Degree Heat

Tine Temperature Time Temperature
10:10 start 1:28 Start
10:17 735 1:33 450
20:25 825 1:38 605
10:80 953 1:43 710
19:35 983 1:48 795
10:40 1065 1:53 920
10:45 1166 1:58 1080
10:80 1260 8:03 1180
10: 56 1350 2808 1300
11:00 1395 2:13 1365
11:05 1460 2:18 1405
21:10 1535 £2325 1425
11:15 1560 2: 28 1450
21; 20 1565 2:55 14365
£:38 1425
2:43 1430
TABLE NUMBER X

Test results for Gear number twelve.

52

 

AV. AV. Growth AV. Growth Total
No. Diam. Diam. dur - Dian. dur - Growth
of after after ing after ing after
Gear Carbur- lst lst end end Carbur-

12 ing. heat heat. heat. heat. izing e
12 6.9837 6.9912 Second heat not run.

1550 Degree Heat

Lime
1:20
1:25
34:30
1:35
1:40
1:45
1: 50
1:55
2:00
2:05
2:10
2:15
2; 20
2:26

Temperature
Start
435
600
680
700
736
775
612

850
885
915
975

1015
1060

Time
2:30
2:35
2:40
2:45
2: 50
2:55
3:00
3:02
3:05
3:10
35:15
3:20

(Cont inued )

Temperature
1110
1150
1190
1225
1255
1290
1310
1325
1450
1550
1560
1550
53

Chapter V
CONCLUSIONS.

The results obtained from the tests run
in the electric furnace have showm that our theory
was applicable when a piece of steel of regular
shape was used. By changing the rates of heating,
as given in our hypothesis, such a piece of steel
can be made to shrink or grow as desired. Also the
time rate of heating may be so regulated that there
will be no change in size during the entire process.
This hypothesis, however, did not hold true for the
entire gear which grew in spite of the time rating
of its heating. It was decided that this growth was
due largely to the peculiar shape of the gear. The
inner web being of moh smaller section that the
rest of the gear, was bound to coool first and become
rigid before this larger part. Consequently, the
larger portion, tending to shrink inwards upon
cooling, will be prevented from doing so by the already
rigid web. Hence, ita effect will be to cause
considerable warping both of the web and of the face
of the teeth, and as far as is now known this is the
real trouble which the Reo has been having with its
gears. A further investigation would require a method
of quenching by which the web would cool after the

heavier part had cooled. This would mean a reversal
 

 

 

 
of the present order of cooling for each part of
the gear.

A quenching fixture almilar to one in use
at the Cadillae Motor Car Co., was therefore
designed ta accemplish this. Its oconstruotion is
shown in the accompanying blue print. ‘The spindle
A remains screwed to the base B at ell times and
is integral with it in the fixture. Radial outs
are made with the saw around the base avy shown.

The steal ring 0 is loose on the spindle. fhe

split plate H and the solid plate I are held te

the east iron block E by means of the shoulder
belts. <A alight inward and outward movement is
permitted the sections of the split plate by means
of the slots in which the shoulder belts fit. The
heavy springs ¥ previde automatic adjustment between
the block 8 and the cone sleeve G. fhe plate I
gives a wearing surface between the split plate and
the block. It also prevents the cone from dropping
from the blook. fhe pine K are inserted for the
purpose of keeping the various sections of the split
plate in their proper position. The handle L is
eagt integral with the cast iron blook. A tapered
wedge D looks the two parts of the Aiture together,
by being driven inte the slot in the spindle.
55

The manner of quenching with this fixture is
as follows. The hot gear is lowered over the spindle
and slipped over the ring C. ‘The upper mrt of the
fixture is lowered by its handle and locked te the
tep of the gear by driving in the tapered wedge.
Part of the presmre thus exerted is transmitted
through the block and springs to the cone which, in
turn, transmits it at right angles through the split
Plate against the inside edge of the heevy part of
the gear. Pressure is also exerted vertically upon
the web of the gear. The fixture is lifted by its
handle and immersed in 011. ‘The saw cuts in the base
give free access of the o11 to the back of the gear,
and at the same time the teeth are entirely surrounded
by the oil. ‘The inner web, being covered with mtal,
is not touched by the o11 and remains hot after the
rest ef the gear has cooled. Therefore the gear is
not prevented from becoming smaller in diameter,- as
was done heretofore. any tendenag to warp is frustrated
by the positive grip of the split plate whioh also keeps
the gear round. The fixture is than taka from the oil,
the tapered wedge removed, amd the upper portion lifted
off. The slip ring is pressed from the gear which has
shrunk tightly upon it.
| This fixture is being made at the xeo tool
room and, if time permits, the results of the tests
run with the fixture will be inserted in this thesis.

56
37

BIBLIOGRAPHY

Albert Sauvenr:- fhe Metallography and Heat freat-

ment of Iron and Steel.

Denison Ke. Baullens:- steel and Its Heat freatment.

Bradley steughten:- fhe Metallurgy of Iron and Steel.

Henry M. Howe:- ‘The Metallurgy of steel and Cast Iron.
 

 

 

 

 

 
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