ABSTRACT

The study was aimed at enhancing the utilization of a blend of recycled engine oil and ash as an appropriate quenchant for the austempering heat treatment of mild steel. The objectives of the study were to utilize Response Surface Methodology to create a model for efficient use of the mixture as a quenchant, determine the optimal process parameters (time and temperature) for austempering with the mixture and develop a predictive model to guide the austempering process in achieving specific desired properties in mild steel. The experimental was designed with Minitab resulting to 27 experimental runs. The independent variables were temperature and time to determine the hardness, impact energy and maximum load. The result showed that maximum hardness of 190BHN, impact energy of110J and maximum load of 6500W. The optimization studied gave hardness value of 176.870, impact energy of 60.1852 and maximum load of 5964.81 at temperature of 870⁰C and time of 27.7773mins with desirability of 1. It was concluded from the studies that using the optimal austempering time and temperature for achieving specific mechanical properties suitable for a particular application can save cost of production by reducing energy cost.

TABLE OF CONTENTS

Cover page

Declaration                                                                                                                              i

Certification                                                                                                                            ii

Dedication                                                                                                                              iii

Acknowledgment                                                                                                                   iv

Table of contents                                                                                                                    v

List of tables                                                                                                                           vii

List of figures                                                                                                                         viii

Abstract                                                                                                                                  ix

CHAPTER ONE

INTRODUCTION

1.0       Background of Study                                                                                                1

1.1       Statement of problem                                                                                                2

1.2       Aim and Objectives of Study                                                                                    3

1.3       Justification of Study                                                                                                3

1.4       Scope of the Study                                                                                                    4

CHAPTER TWO

LITERATURE REVIEW

2.1       Mild Steel                                                                                                                   5

2.2       Heat Treatment of steel                                                                                              5

2.2.1    Austempering                                                                                                              8

2.2.2.1 Practical Factors Affecting Successful Austempering                                             10

2.2.2    Quenching                                                                                                                  14

2.2.3    A mixture of used engine oil and ash as quenching                                                  14        

2.3       Response surface methodology                                                                                 14        

2.3.1    Objectives and typical application of RSM                                                               16

2.4       Review of similar literature                                                                                        17

CHAPTER THREE

MATERIALS AND METHODS

3.1       Materials                                                                                                                     19

3.1.1    Software Requirement                                                                                                19       

3.2       Method                                                                                                                       19

3.2.1    Experimental procedure                                                                                              19

3.2.2    The model summary table                                                                                           20

3.2.3    Metallographic Investigation                                                                                      21

CHAPTER FOUR

RESULTS AND DISCUSSION

4.1.      Experimental results                                                                                                    22

4.2.      Effect of Time                                                                                                            23

4.3.      Effect of temperature                                                                                                 24

4.4.      Response surface analysis result                                                                                 25

4.4.1    ANOVA Results                                                                                                        26

4.4       Optimization Studies                                                                                                  33

CHAPTER FIVE

CONCLUSION AND RECOMMENDATIONS

5.1       Conclusion                                                                                                                   35

5.2       Recommendation                                                                                                        35

REFERENCES

LIST OF TABLES

Table 2.1 Physical Properties of Mild Steel                                                                            5

Table 3.2 Summary of Experimental Parameters                                                                    20 Table 3.3 Samples Description                                                                                       20

Table 4.1: Experimental result                                                                                                25

LIST OF FIGURES

Figure 2.1        Effect of alloying element on the carbon content of the eutectoid composition 7

Figure 2.2        Microstructure Showing Supersaturated Carbide and Ferrite                                    9

Figure 2.3        Microstructures of Austempered Mild Steel at 300, 350 and 400                 10       

Figure 2.4        Effect of austempering temperature on the properties of ductile iron            13

Figure 4.1:       Effect of time and temperature on hardness                                                  22

Figure 4.2:       Effect of time and impact energy on Toughness                                            23

Figure 4.3:       Effect of time and maximum on tensile strength                                           23

Figure 4.4:       Effect of temperature on the hardness                                                           24

Figure 4.5:       Effect of temperature on the impact energy                                                   24

 Figure 4.6:     Effect of temperature on the maximum load                                                  25