THE EFFECTS OF HEAT TREATMENT ON THE MECHANICAL PROPERTIES OF A WELDED JOINT OF MEDIUM CARBON STEEL

ABSTRACT
The effect  of Heat treatment on the Mechanical Properties of a welded joint of medium carbon steel has been carried out.  The materials were cut, welded, to get 27 samples needed. Thereafter, Heat Treatment was carried out on the samples. Then the specimens were grouped into two groups, group A and group B. In group  A, after the heat treatment on the welded specimens, one sample was quenched in water immediately, another was oil-quenched and the third one was allowed to cool under still air. In group B, 25 specimens were heated to 9100C (Austenitic temperature) and were divided into two. Remaining one  in the furnace was removed and allowed to  cool under still air. 12 sample were quenched in water, tempered at different temperature as follows 2500c, 4500c, 6600c, and quenched at different time interval, 30,60,90, 120 and the same process was applied to the oil-quenched specimens. One was brought out from each specimen that were water-quenched and oil-quenched. Then the remaining one in the furnace was removed to cool under still air. From group A and group B, 6 Samples was prepared for testing. Hardness test and Microstructure test were carried out on the experimental specimens. The result showed that the hardness decreases as the temperature and time increases. The Microstructureal  test revealed that the structure of welded joint of medium carbon steel could be well refined by heat treatment. 




TABLE OF CONTENTS
Title page
Approval page
Dedication
Acknowledgment
Abstract
Table of contents
CHAPTER ONE
1.0  INTRODUCTION
1.1 Welding
1.1.1 Arc Welding Processes
1.1.2 Oxy Gas Welding Processes 
1.1.3 Structural Changes In Steel During Welding.
1.1.4 Welded Joint 
1.1.5 Types Of Welded Joints Are
1.1.6 Butt Welded Joint
1.1.7 Types Of Butt Welded Joints:
1.1.8 Corner Welded Joints
1.1.9 Edge Welded Joint
1.1.10 Lap Welded Joint
1.1.11 Tee Welded Joints
1.1.12 Method of Welding Tee Joint
1.1.14 Inclusions 
1.1.15 Cracking
1.1.16 Under Cut
1.1.17.Lamellar Tearing
1.2 Aims and Objectives Of This Project Work  


CHAPTER TWO
2.0 LITERATURE REVIEW
2.1steel                                                                                                                                                              2.1.1 Types Of Steel
2.1.2 Weldability
2.1.3 The Heat Treatment Of Steels   
2.1.4 Hardening Of Steel
2.1.5 Different Quenching Media
2.2 Tempering            
2.2.2 Annealing
2.3 Grain Size
2.4.1 Structure Changes In Steel During Heat Treatment
2.4.2 Testing Of Materials
2.5 Hardness Test
CHAPTER THREE
EXPERIMENTAL PROCEDURE
3.1    Sourcing of The Material
3.2 Preparation of the Materials For Welding
3.3 Welding of the Specimens
3.3.2 Weld Procedure
3.3 Heat Treatment Process
3.4 Heat Treatment Procedure
3.4.1 Hardness Testing
3.4.2 Hardness Procedure
3.5 Microstructrue Test.
3.5.1 Micro Graph Procedure
CHAPTER FOUR
4.0  MECHANICAL TEST
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.0     Conclusion
5.1 Recommendations
  References


LIST OF FIGURES
Figure 1:         Welded medium carbon steel
Figure 2.1:     Equilibrium Phase Diagram
Figure 2.2         Temperature –time transformation diagram
Figure 3.1:      Square steel bar