eas107 lab 1

Mohd Ashraf Mohd Ismail

Laboratory Experiment 1

Name : Mohammed Ashraf Bin Mohammed Ismail

Student No: N0806406

Contact No: 98225529

Date Submitted:

Lab. : Heat Treatment for Steel

Course Instructor: Mr Lecturer

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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

Introduction to Introduction to Engineering Material and Aeromaterial

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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).


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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.


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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)


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Experim

ent Reading

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Experimental Data

Hardness Test Graph

Toughness Test


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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


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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

eas107 lab 1

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