Laboratory

 Experiment  1  

Mohd  Ashraf  Mohd  Ismail  

 

Name : Mohammed Ashraf Bin Mohammed Ismail

Student No: N0806406
Contact No: 98225529
Date Submitted:
Lab. : Heat Treatment for Steel
Course Instructor: Mr Lecturer
   
Table of Contents
ABSTRACT .................................................................................................................. 3

INTRODUCTION ......................................................................................................... 4

HEAT TREATMENT PROCESS ................................................................................. 6

OBJECTIVES................................................................................................................ 7

EXPIREMENT PROCEDURE ..................................................................................... 8

EXPIREMENT RESULT............................................................................................ 10
Hardness Test....................................................................................................... 11
Impact Test .......................................................................................................... 11
Microstructure of the different Test result........................................................... 12

DISCUSSION OF RESULT........................................................................................ 13

CONCLUSION............................................................................................................ 14

REFERENCE .............................................................................................................. 15

APPENDIX.................................................................................................................. 16

2    
Abstract
The heat treatment behavior of tool steel (AISI 01) and Carbon Steel (1045) is
investigated. In this experiment, the effects of quenching , tempering and annealing
are being studied and how it affects the formation and decomposition of austenite
martensite, ferrite and other phase of steel. The experiment makes extensive use of the
Fe-Fe3 C equilibrium phase diagram. The results of the teat treatment are evaluated
using the Rockwell Hardness Test and impact test. The analysis of the microstructure
of each specimen is also being carried out.

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Introduction
Iron is the most widely use material in the world. In the history of civilization, they
make their mar by defining the IRON AGE.
Pure Iron is very soft and weak and does not possess sufficient strength and hardness
to be used in many engineering application
Heat Treatment is often associated with increasing the strength of material, but it can
also be used to alter certain manufacturability objectives such as improve machining,
improve formability, restore ductility after a cold working operation. Thus it is a very
enabling manufacturing process that can not only help other manufacturing process,
but can also improve product performance by increasing strength or other desirable
characteristics.

Iron is an allotropic element that is it can exist in more than one physical form. At
room temperature, iron has a Body Centered Cubic Structure (BCC) and upon heating
to above 910˚C, it’s structure changes to Face Centered Cubic Structure (FCC)
Steel is an alloy consisting mostly of iron, with carbon content between 0.2% and
2.04% by weight, depending on grade. Carbon is the most cost-effective alloying
material for iron, but various other alloying elements are used such as manganese,
chromium, vanadium, and tungsten. Steel with increased carbon content can be made
harder and stronger than iron, but is also more brittle.
Five main constituents of Steel:
Ferrite- The structure of pure iron. Has a body-centred cubic (BCC) crystal structure.
It is soft and ductile and imparts these properties to the steel. Very little carbon (less
than 0.01% carbon will dissolve in ferrite at room temperature).
Austenite- Is the structure of iron at high temperatures (above the upper critical
range).Has a face-centre cubic (FCC) crystal structure. It contains a maximum of
0.83% carbon at 723°C. It properties are very soft, ductile and non-magnetic. It is not
present at room temperatures.
Cementite - A compound of iron and carbon, iron carbide (Fe3C). It is hard and brittle
and its presence in steels causes an increase in hardness and a reduction in ductility
and toughness.
Pearlite - A laminated structure formed of alternate layers of ferrite and cementite It
combines the hardness and strength of cementite with the ductility of ferrite and is the
key to the wide range of the properties of steels. The laminar structure also acts as a
barrier to crack movement as in composites. This gives it toughness.
Martensite - A very hard needle-like structure of iron and carbon. Only formed by
very rapid cooling from the austenitic structure (i.e. above upper critical temperature).

4    
  

Figure  1  -­  Steel  Equilibrium  Phase  Diagram

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Heat Treatment of Steel
Heat treatment is to produce material with desired mechanical properties by
controlling the formation of their microstructure, which includes Grain size, Grain
Shape and Phase distribution without changing the product shape.

There are 4 main type of heat treatment process:

 Annealing – Involve heating the steel to about 50

ºC (above the Austenitic temperature line (A3) )It
is held at this temperature for sufficient time for
all the material to transform into Austenite. It is
cooled very slow controlled furnace cooling(20
ºC/hr ) till room temperature. The grain structure
has coarse Pearlite with ferrite or Cementite
(depending on whether hypo or hyper eutectoid).
The steel becomes soft and ductile.

 Normalizing – Heating the steel at a suitable temperature (723˚C) above the

transformation stage, holding it there for a period of time) and letting it cooled
slowly in still air to room temperature. It allows the steel to cool more rapidly
than annealing thus producing fine pearlite. It has a more uniform grain
structure, reduces segregation and improve mechanical properties

 Hardening – Heating the steel to the required temperature for change in

structure within the material to occur and holding it long enough for entire
material to undergo the structural change. It is then cooled rapidly or quench
in water, oil or some suitable solution. When steel is heated above the upper
critical temperature the iron crystal structure will change (FCC), and the
carbon atoms will migrate into the central position formerly occupied by an
iron atom(austenite). If this steel form cools slowly, the iron atoms move
back into the cube forcing the carbon atoms back out, resulting in soft steel
called pearlite. If the steel is cooled rapidly (quench) , the carbon atoms are
trapped, and the result is a very hard, brittle steel. This steel crystal structure
is now a body centered tetragonal(BCT) form called martensite. Severe
quenching can lead to cracking.
 Tempering -Tempering is done immediately after quench hardening. The part
is reheated to a temperature of 150 to 400 ºC (we use 350ºC -Lead Bath))
After reaching the desired temperature, the parts are held at that temperature
for about 1 hour, then removed from the bath and cooled in still air.
The process of reheating the steel leading to precipitation and spheroidisation
of the carbides. When heated, the Carbon atoms diffuse from Martensite to
form a carbide precipitate and the concurrent formation of Ferrite and
Cementite, which is the stable form. (Not suitable of carbon steel)The negative
effects are the reduction of the martensite (BCT) structure and the progression
towards a spheroidal carbide + ferrite matrix structure. The benefits resulting
are the increase in the metal toughness and elongation.

6    
Objectives
From the experiment we were able to :

I. Effect of alloying elements on hardness of steel.

II. Effect of cooling rate on Eutectoid transformation

III. Tendency for crack with severe quench and how to reduce the quench crack

IV. Improve Toughness

V. Compare properties for pearlite, martensite, tempered martensite and bainite.

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Experimental Procedure
Step 1 – We heat the specimens to as per specification below

We use 6 specimens each (Tool Steel and Carbon Steel) for the experiment. We
detonate (T) for Tool Steel and (C) for Carbon Steel

Speciment1 – Original State (Unchanged)

Speciment2 – Heat up to 800°C for 1 hrs, immediately quench in water till

material reach room temperature (Quench in Water)

Speciment3 – Heat up to 800°C for 1 hrs immediately quench in oil till material
reach room temperature. (Quench in Oil)

Speciment4 – Heat up to 800°C for 1 hrs immediately air cooled till room
temperature (Normalizing)

Speciment5 – Heat up to 800°C for 1 hrs, immediately quench in lead

bath(300°C) for 45 sec and then air cooled till room temp. (Austempering)

Speciment6 – Heat up to 800°C for 1 hrs, immediately quench in lead

bath(300°C) for 45 min and then air cooled till room temp.(Martempering)
Step2)  -­‐  After  heating  up  in  the  furnace  and  cooling  the  specimens  material  to  
room  temperature  we  did  the  hardness  test    The  hardness  test  we  did  was  using  
the  Rockwell  Hardness  Test  (HRC)  16mm  diamond  tip.  

Step  3  )Check  for  any  visible  cracks    

Step  4)  Only  after  all  the  necessary  has  been  recorded  we  proceeded  to  do  the  
impact  test    

Step  5)  After  the  specimen  has  been  broken,  we  further  cut  it  into  smaller  piece  
and  then  mould  it  into  a  plastic  holder.  After  than  we  proceeded  with  polishing    
the  specimen  so  that  we  can  have  a  clearer  picture  when  we  analysis  their  
microstructure    

Step  6)  Taking  picture  of  the  individual  specimen  microstructure  using  the  high  
magnification  microscope    

Step  7)  Tabulate  all  the  data  into  a  table  form  and  for  clearer  comparison  we  also  
plotted  graphs.  

The  two  type  of  carbon  steel  used  for  this  experiment  are:  

- AISI  1045  is  a  medium  carbon  steel  containing  about  0.45%  carbon    

- AISI  01  is  a  high  carbon  steel  containing  about  0.9  %  carbon  (  oil-­‐
hardening)  
8    
  

Experiment Reading

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Experimental Data  
Hardness Test Graph

Toughness Test

10    
Picture of Specimen Microstructure ( X 200 times)

  Tool  Steel   Carbon  Steel  

Specimen  1  

Original  
   

Specimen  2  

Quench  in  water  

   

Specimen  3  

Quench  in  oil  

   

Specimen  4  

Normalizing  
   

Specimen  5  

Austempering  
   

Specimen  6  

Martempering  
   

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Discussion of Result  

12    
Conclusion
Heat  treating  is  important  to  us  because  it  is  an  easy  way  to  improve  metals  and  
make  them  more  versatile.  This  is  important  because  one  of  the  greatest  
qualities  a  material  can  have  is  that  it  is  useful  or  can  be  used  for  many  purposes.  

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Reference
1) http://www.efunda.com/processes/heat_treat/introduction/heat_treatments.cfm
2) http://en.wikipedia.org/wiki/Carbon_steel
3) http://www.roymech.co.uk/Useful_Tables/Matter/Hardening.html
4) http://info.lu.farmingdale.edu/depts/met/met205/heattreating.html
5) http://www.steel.org//AM/Template.cfm?Section=Home

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