The document discusses the Jominy end quench test, which is used to measure the hardenability of steels. In the test, a cylindrical steel sample is uniformly heated, then quenched at one end with water to rapidly cool it. Hardness measurements are then taken at intervals along the sample's length from the quenched end. The results show decreasing hardness further from the quenched end, indicating how deep within the material the heat treatment can harden it. Alloying elements like chromium, molybdenum, and manganese can shift the hardness "nose" deeper, improving hardenability by slowing the transformation of austenite. The test provides critical information for selecting ste

1. Tejas Atyam
III Sem- BE (Prod.)

2. Hardenability
 One of the important properties of (processed) metals is
hardenability
 Hardenability is the capability of an alloy to be
hardened by heat treatment
 Measures the depth of hardness obtained by heat
treatment/quenching
 Hardenability is not the same as hardness.
 The Hardness of a steel refers to its ability to resist deformation when a
load is applied, whereas hardenability refers to its ability to be
hardened to a particular depth under a particular set of conditions.

3. Jominy Test
 The Jominy End Quench Test measures
Hardenability of steels.
 As we already discussed, hardenability is a measure of
the capacity of a steel to be hardened in depth when
quenched from its austenitizing temperature.

4. Why Jominy Test?
 Information gained from this test is necessary in
selecting the proper combination of alloy steel and
heat treatment to minimize thermal stresses and
distortion when manufacturing components of various
sizes.

5. Steps to conduct Jominy Test
1. First, a sample specimen cylinder either 100mm in length and 25mm
in diameter, or alternatively, 102mm by 25.4mm is obtained
2. Second, the steel sample is normalized to eliminate differences in
microstructure due to previous forging, and then it is austenitised.
This is usually at a temperature of 800 to 900°C.
3. Next, the specimen is rapidly transferred to the test machine, where
it is held vertically and sprayed with a controlled flow of water onto
one end of the sample
4. This cools the specimen from one end, simulating the effect of
quenching a larger steel component in water
(Because the cooling rate decreases as one moves further from the quenched
end, one can measure the effects of a wide range of cooling rates from very
rapid at the quenched end to air cooled at the far end.)

6. Steps to conduct Jominy Test
….. Contd…
5. Next, the specimen is ground flat along its
length to a depth of .38mm (15 thousandths of an
inch) to remove decarburized material.
specimen
(heated to g
phase field)
24°C water
flat ground
Rockwell C
hardness tests
6. The hardness is measured at intervals along its length
beginning at the quenched end. For alloyed steels an
interval of 1.5mm is commonly used where as with carbon
steels an interval of .75mm is typically employed.

7. Steps to conduct Jominy Test
….. Contd…
7. And finally the Rockwell or Vickers hardness values are plotted
versus distance from the quenched end.
Hardness versus distance from the quenched end
Hardness, HRC
Distance from quenched end
 The Jominy Test data illustrates the effect of alloying and
microstructure on the hardenability of steels.

8. End-Quench hardenability test
(Jominy Test) - Summary
 Quenching media
 Water
 Brine
 Oil
 Molten salts
 Air
 Caustic solutions
 Polymer solutions
 gases
 Round test bar is
austenized (heated to
the proper temperature
to form 100% austenite)
 Bar then quenched at
one end
 Hardness decreases away
from the quenched end
of the bar

9. Commonly used elements that affect the hardenability of steel are
carbon, boron, Chromium, Manganese, Molybdenum, Silicon, and
Nickel.
 Carbon is primarily a
hardening agent in
steel, although to a
small degree it also
increases hardenability
by slowing the formation
of pearlite and ferrite.
But this affect is too
small to be used as a
control factor for
hardenability.
 Boron can be an
effective alloy for
improving
hardenability at levels
as low as 0005%.
 Boron is most effective in
steels of 0.25% Carbon or
less.

10. And Finally
 Slowing the phase transformation of austenite to
ferrite and pearlite increases the hardenability of
steels.
 Chromium, Molybdenum, Manganese, Silicon,
Nickel and Vanadium all effect the hardenability of
steels in this manner.
 Chromium, Molybdenum and Manganese being used
most often.

11. 11
Why Hardness Changes with Position
• The cooling rate varies with position.
distance from quenched end (in)
Adapted from Fig. 11.13, Callister 7e.
(Fig. 11.13 adapted from H. Boyer (Ed.)
Atlas of Isothermal Transformation and
Cooling Transformation Diagrams,
American Society for Metals, 1977, p.
376.)
Hardness, HRC
60
40
20
0 1 2 3
T(°C)
600
400
200
M(start)
A M
0.1 1 10 100 1000
Time (s)
0
0%
100%
M(finish)

12. Hardenability vs Alloy Composition
12
• Jominy end quench
results, C = 0.4 wt% C
Adapted from Fig. 11.14, Callister 7e.
(Fig. 11.14 adapted from figure furnished
courtesy Republic Steel Corporation.)
• "Alloy Steels"
(4140, 4340, 5140, 8640)
--contain Ni, Cr, Mo
(0.2 to 2wt%)
--these elements shift
the "nose".
--martensite is easier
to form.
Cooling rate (°C/s)
Hardness, HRC
60
40
20
100 10 3 2
100
4340 80
%M
50
4140
8640
5140
0 10 20 30 40 50
Distance from quenched end (mm)
800
T(°C)
600
400
200
shift from
A to B due
to alloying
M(start)
M(90%)
10-1 10 103 100 5
Time (s)
A B
TE

13. 13
Quenching Medium & Geometry
• Effect of quenching medium:
Medium
air
oil
water
Severity of Quench
low
moderate
high
Hardness
low
moderate
high
• Effect of geometry:
When surface-to-volume ratio increases:
--cooling rate increases
--hardness increases
Position
center
surface
Cooling rate
low
high
Hardness
low
high

14. Jominy Test Dimensioning Jominy Test Apparatus
Used Jominy Test Piece Jominy Results exmaple