ABSTRACT

In this research work the improvement of the mechanical properties of mild steel by the heat treatment methods of austenitizing and austempering using locally sourced plantain stem extracts was investigated. The austempering process parameters studied were austempering temperature, austempering time, and austempering bath concentration as the plantain stem extract used to heat treat mild steel can have a number of beneficial effects. It can increase the strength and hardness of the steel, making it more resistant to wear and tear. It can also improve the corrosion resistance of the steel, making it more durable and less prone to rusting. The mechanical properties of the mild steel quenched in plantain tree extract were evaluated using tensile strength, hardness, and impact toughness tests. The results showed that the austempering temperature and time had a significant effect on the mechanical properties of the mild steel

From the result on an investigation conducted on mild steel and austempered in a range of time and temperature. The tensile strength was found to increase with increasing austempering temperature with maximum tensile strength seen in samples austempered at temperature of 340°C. Hardness of the samples was found to be decreasing with increasing austempering time and decreasing austemperimg temperature, and toughness of mild steel was seen to be increasing with increasing time and temperature and was more prominent in samples austempered at a temperature of 300°C.

                                         

 TABLE OF CONTENTS

Title page                                                                                                                                i

Declaration                                                                                                                              ii

 Certification                                                                                                                           iii

Dedication                                                                                                                              iv

Acknowledgment                                                                                                                   v

Table of Contents                                                                                                                   vi

Lists of Tables                                                                                                                         ix

Lists of Plates                                                                                                                          x

List of Figures                                                                                                                         xi

Nomenclature                                                                                                                          xii

Abstract                                                                                                                                  xiii

 

CHAPTER ONE: INTRODUCTION

1.0       Background of Study                                                                                                 1

1.1       Statement of Problem                                                                                                 3

1.2       Aims and Objectives                                                                                                   3

1.3       Justification                                                                                                                 3         

 

CHAPTER TWO: LITERATURE REVIEW

2.1       Mild Steel                                                                                                                   4

2.2       Heat Treatment Of Steel                                                                                             4

2.2.1    Austempering                                                                                                  5

2.2.2    Quenching                                                                                                       5

2.2.3    Plantain Stem Extract as Quenchant                                                              5

2.3       Response Surface Methodology                                                                                 6

2.3.1    Objectives and Typical Application of RSM                                                  7

2.4       Review of Similar Literature                                                                                      8

CHAPTER THREE: MATERIALS AND METHODS

3.1       Materials                                                                                                                     11

3.1.1    Equipment for Heat Treatment and Mechanical Testing                                11

3.1.2    Software Requirement                                                                                    11

3.2       Methodology and Analysis                                                                                         12

3.2.1    Experimental Procedure                                                                                  12

3.2.1.1 Extraction of Fluid from Plantain Tree                                                           12

3.2.1.2 Heat Treatment                                                                                               12

3.2.1.3 Tensile Test                                                                                                     14

3.2.1.4 Hardness Test                                                                                                 16

3.2.1.5 Impact Test                                                                                                     17

3.2.1.6 Metallographic Investigation                                                                          19

 

CHAPTER FOUR: RESULTS AND DISCUSSION

4.1       Result                                                                                                                          20

4.1.1    Hardness Test Result                                                                                      21

            4.1.2    Impact Test Result                                                                                         22

            4.1.3    Tensile Test Result                                                                                          23

4.2       Response Surface Regression Result                                                                          25

            4.2.1 Response Surface Regression: Hardness (BHN) versus Temperature, time     26

            4.2.2 Response Surface Regression: Impact Energy (J) versus Temperature, time   28

            4.2.3 Response Surface Regression: Max Load (Mpa) versus Temperature, time    30

            4.2.4    Interpreting the Response Surface Regression Models                                  32

            4.2.4.1 Residual Plots                                                                                                 32

            4.2.4.2 Table of Coefficients                                                                                      33

            4.2.4.3 The Model Summary Table                                                                             33

4.3      Response Optimization                                                                                                35

4.4      Graphical Analysis                                                                                                       36

            4.4.1    Contour Plots                                                                                                  36

            4.4.2    Factorial Plots                                                                                                 38

            4.4.2.1 Main Effect Plot                                                                                             38

            4.4.2.2 Interaction Plot                                                                                               40

            4.4.3    Surface Plot                                                                                                    41

CHAPTER FIVE: CONCLUSION AND RECOMMENDATION

5.1       Conclusion                                                                                                                  43

5.2       Recommendation                                                                                                        43

 

References                                                                                                                              44

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LISTS OF TABLES

Table 2.1:        Physical Properties of Mild Steel                                                                    4      

Table 3.1:        Chemical Composition of Mild Steel                                                              11

Table 3.2:        The Austempering Window                                                                            14

Table 3.3:       Samples Identification                                                                                     14

Table 4.1:        Hardness Values for Mild Steel                                                                      21

Table 4.2:        Toughness Values for Mild Steel                                                                    22

Table 4.3:        Tensile Values for Mild Steel                                                                         23

Table 4.4:        Table of Experimental Results                                                                        25

Table 4.5:        Comparing Predicted and Experimental Values                                             34

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF PLATES

Plate 3.1          Tensile specimen specification                                                                        15

Plate 3.2          Tensile Test Apparatus                                                                                    16

Plate 3.3          Hardness Apparatus                                                                                        17