Islamic University Of Gaza
Faculty of Engineering
Dept. of Industrial Engineering
MANUFACTURING (lab)
EX#(1)
Heat Treatment
Student : Mohammed Al Kurd
Number :120050264
Engineering : Abd Al Rahman Al Haj
DATE :14/03/2006
Contents :
List of table ………..…………………………..………...….….3
Abstract ……………...…………………..………...………..….4
Objective …………………………...………………….….……5
Background ……………………...…………………………......5
Procedures ……………………….………………….....……….6
Results ………………………………………….......…………..7
Comment ……….…..……………………………….…...…..…9
List of Tables
TABLE 1: hardness reading ………………..………….....…………..7
List of figures
Fig1: carbon-iron system ………………………….…………..……..8
Abstract:
Heat treatment processes can improve many properties of materials like strength,
hardness, ductility, toughness, and resistance to wear.
Heat treatment modifies microstructure and , thereby, produces a variety of
mechanical properties that are important in mfg such as improved formability and
machinability
As we know carbon-iron system are composite from Ferrite, Autenite and Cementite
Austenite is an important phase in the heat treatment of steels and has maximum
solubility of 2.11% C at 1148o C.
Austenite is not stable when alloyed by carbon alone below 727o C and nonmagnetic.
Objectives:
1. To obtain an understanding of the effects of hardening process (by heat treatment)
on certain properties of engineering metals and alloys.
2. To obtain an understanding of the effects that quenching medium and tempering
temperature will have on the hardness of hardened parts.
Background:
Iron is one of the oldest known metals, and carbon is the cheapest and most effective
alloying element for hardening iron. Carbon steels account for more than 70% of the
tonnage of metallic materials used in the United States for engineering applications.
Carbon is added to iron in quantities ranging from 0.04 to 2 wt% to make low,
medium, and high carbon steels. The microstructure and resulting mechanical
properties of these steels are amenable to modification via heat treatment, and a wide
range of mechanical properties can be obtained by proper variations of heating and
cooling cycles. Modest amounts (up to a few wt% percent each) of costlier alloying
elements such as nickel, chromium, manganese, and molybdynum can be added to the
composition, resulting in “low alloy” [content] steels that possess additional desirable
properties, including achievability of high strength and good ductility in larger
sections.
Some common heat treatments for low and medium carbon steels:
1. Austenitize and Air-Cool:
This is the typical heat treatment given to the steel by the manufacturer, and is
accordingly termed the as received condition. The thermal history leading to this state
is also called normalizing. Normalizing of 1045 steel typically consists of the
following steps:
• Austenitize: put in furnace at 850C in the austenite range, and hold for 1 hour until
equilibrium temperature and corresponding solid solution structure have been
reached.
Air-cool: remove from furnace and allow air-cooling to room temperature.
2. Austenitize and Furnace Cool:
This heat treatment is sometimes also called annealing. Here the steel is subjected to
the following temperature histories:
Austenitize: put in furnace at 850C in the austenite range, and hold for 1 hour until
equilibrium temperature and corresponding solid solution structure have been
reached.
Furnace Cool: slowly cool in the furnace, from 850C to 700C, over a period of 10
hours.
Air-cool: remove from furnace and allow air-cooling to room temperature.
Austenitize and Quench:
Austenitize: put in furnace at 850C in the austenite range, and hold for 1 hour until
equilibrium temperature and corresponding solid solution structure have been
reached.
Quench: Rapidly remove material from furnace, plunge it into a large reservoir of
water at ambient temperature, and stir vigorously. For 1045 steel, the quenching
medium is water at ambient temperature (for other steels, other quenching media such
as oil or brine are used).
3. Austenitize, Quench, and Temper:
Austenitize: put in furnace at 850C in the austenite range, and hold for 1 hour until
equilibrium temperature has been reached.
Quench: Rapidly remove material from furnace, plunge it into a large reservoir of
water at ambient temperature, and stir vigorously.
Temper: Reheat the steel to the tempering temperature (example: 250C), and hold for
approximately 2 hours. Note: there is a range of possible tempering temperatures; for
1045 steel, this range is approximately from 200C to 500C. Different tempering
temperatures lead to differences in the resulting mechanical properties; in general,
‘lower’ tempering temperatures lead to high yield strength, but lower toughness and
ductility, while ‘higher’ tempering temperatures lower strength, but increase
toughness and ductility.
Air-cool: remove from furnace and allow air-cooling to room temperature.
Each of these thermal histories produces unique microstructural conditions in the
steel, and in turn, each microstructural state exhibits a unique combination of
mechanical properties. We will perform the heat treatments, and measure the resulting
mechanical properties.
Procedures:
1. Prepare two reservoirs with water for the first and brine (salt water) for the
other.
2. Cut four sample pieces of AISI 1045 carbon steel and mark each piece.
3. Anneal the samples (heat them to austenitizing temperature then turn the
furnace off letting them cool slowly inside it).
4. Take the average hardness for each sample.
5. Austenitize the samples again and then quench two of samples in the water
medium and the others in the brine.
6. Take the average hardness for each sample.
7. Temper the samples quenched in water at two different temperatures (300, and
500), and do the same with others quenched in brine.
8. Take the average hardness for each sample.
Hardness Readings (HRC) for the four specimens which were
heat treated in the experiment:
Part number
Hardness HRC
(after
annealing)Average HRC
Quenching in
Hardness HRC
Average HRC
Tempering at
Hardness HRC
Average HRC
1
17.3
21.5
20.2
19.7
Brine (8% salt)
58.9
61.6
59.4
60
300 oC
51.2
52.2
55.5
53
4
19.7
20.7
20.8
20.4
Brine (8% salt)
65
65.7
60.8
63.8
300 oC
51.7
51.4
53
52
2
15.5
17.1
15.9
16.2
Water
53.9
51.4
53.9
53.1
3
17.3
17.2
16.9
17.1
Water
50.1
51.9
50.5
50.8
500 oC
43.1
39.7
39.8
40.9
500 oC
38
37.3
39.4
38.2
Conclusion:
This experiment is a very important for the industrial , manufacture ,and mechanical
engineering because it has a very important principles for the heat treatment process
and its applications and methods , the heat treatment process is very large study , but
as an start the experiment is give as a very important information’s.
There are three types to make material harder: annealing, quenching and normalizing.
Annealing is cooling material in the furnace, normalizing is cooling material in the
air, quenching is raped cooling of material in flood (Brine, water) but it make crack
in material. When we use water only air bubbles will form about apart that make air
field about it and we found some bubbles in metal that decrease hardness so we use
brine (water, salt) to take out the air. Illustrated in the experiment the part that
quenched in water is less hardening than the part that quenched in brine.