Investigation of Edge Cracking Propensity in Cold-Rolled Commercial Aluminium Alloy 8011 under Mixed Oil Lubrication Condition.
ABSTRACT
The effect of iron content on edge cracking tendency in cold-rolled commercial aluminium alloy 8011 under a mixed coconut/diesel oil (factory formulated oil) lubrication condition and under neem seed oil as an alternative has been investigated.
Three different aluminium alloy plates each containing 0.708%Fe, 0.909%Fe and 0.931%Fe were produced by chill casting method. Seven samples each of dimension 240mm x 140mm x 7mm were cast per alloy.
As-received commercial aluminium alloy 8011 of 0.857%Fe was cut into seven samples of the same geometry. Experimentation involved cold reduction in thickness by rolling at various degrees of deformation, followed by testing of mechanical properties and qualitative metallographic analysis.
Performance evaluation of mixed coconut/diesel oil and neem seed oil lubricants in friction reduction of cold-rolled commercial AA 8011 and proportion of mixture of coconut and diesel oil that will give the highest percentage deformation were also conducted by plane strain compression test.
From the results obtained, it was observed that aluminium alloy 8011 generally exhibited softening characteristics as shown by its maximum ultimate tensile strength of 176.45MPa at 60% reduction in thickness and on reaching the peak hardness values, all samples displayed decrease hardness for given levels of percent reduction in thickness.
It was also observed that for up to a maximum of 0.931%Fe, AA 8011 could be cold-rolled to a maximum of 60% reduction in thickness without any evidence of edge cracking. Alloys with 0.909%Fe and 0.931%Fe, edge cracked at 70% and 80% reductions in thickness and the other alloys showed no edge cracking for the whole percentage deformations investigated.
TABLE OF CONTENTS
Title Page….. i
Declaration……… ii
Certification… iii
Dedication…… iv
Acknowledgements…. v
Abstract………. vi
Table of Contents……. viii
List of Figures…… xiii
List of Tables.. xv
List of Plates…… xvi
- INTRODUCTION.1
- Statement of the Research Problem…….. 2
- Justification……… 3
- Aim and Objectives………. 4
- Scope of the Work…… 5
- Contribution to Knowledge………….. 5
- LITERATURE REVIEW…. 7
- Introduction…………………. 7
- Metal Rolling Process……… 7
- Hot-rolling………….. 8
- Cold-rolling……….. 9
- Mechanics of Rolling Process………….. 9
- Pressure Distribution along the Arc of Contact and Roll Bite Condition.. 12
- Problems and Defects in Rolled Products……. 13
- Edge Cracking………… 14
- Causes of Edge Cracking………. 15
- Friction and Lubrication in Metal Working Processes…. 18
- Mode of Lubrication in Cold Rolling………… 19
- Evaluation of Lubricants in Cold Rolling by Plane Strain Compression Test…… 20
- Chemical Analysis of Lubricating Oils……… 22
- Effect of Iron on Aluminium Alloys…… 23
- Effect of Iron on the Mechanical and Structural Properties of Aluminium Alloys………….. 25
3.0 MATERIALS, EQUIPMENT AND GENERAL EXPERIMENTAL PROCEDURES..30 3.1 Introduction.. 30
- Materials…………. 30
- Commercial Aluminium Alloy 8011…… 30
- Mixed Coconut/diesel and Neem Seed Oil……………. 31
- Equipment……. 31
- Experimental Procedures…………. 32
- Casting of Alloys………. 32
- Cold Rolling Experiment……. 33
- Tensile Strength Test… 34
- Hardness Test……. 35
- Impact Strength Test….. 35
- Metallographic Examination……….. 36
- Chemical Analysis of the Investigated Oils….. 36
- Plane Strain Compression Test… 37
- EXPERIMENTAL RESULTS…………… 39
- Introduction……. 39
- Evaluated Mechanical Properties………. 39
- Microstructural Examination of AA 8011…. 40
- Chemical Analysis of the Investigated Oils…………. 41
- Lubrication Potential of the Investigated Oils in Cold Rolling of AA 8011 by Plane Strain Compression Test 42
- DISCUSSION OF THE EXPERIMENTAL RESULTS…… 44
- Introduction…4
- Edge Cracking Characteristics of Aluminium Alloy 8011 of Varying Iron Contents Cold-rolled to Various Reductions in Thickness……….. 44
- Effect of Iron Content on Tensile Properties of Cold-rolled Samples of AA 8011 45
- Effect of Iron Content on Ultimate Tensile Strength of Cold-rolled Samples of AA 8011 47
- Effect of Iron Content on Ductility of the Cold-rolled Samples of AA 8011…… 49
- Effect of Iron Content on Hardness Properties of Cold-rolled Samples of AA 8011…51
- Effect of Iron Content on Impact Strength of Cold-rolled Samples of AA 8011 52
- Effect of Iron Content on Microstructures of Cold-rolled Samples of AA 8011 53
- Evaluation of Lubricants in Cold Rolling Process…. 54
- Evaluation of Proportions of Mixture of Coconut and Diesel Oils in Cold Rolling Process… 56
- SUMMARY, CONCLUSION AND RECOMMENDATIONS…. 58
- Summary….. 58
- Conclusion……. 58
- Recommendations….. 59
REFERENCES.. 61
APPENDICES 68
INTRODUCTION
The rolling of slab or sheet metals is probably one of the most advanced techniques among metal working processes due to its high productivity and close control of the final products.
The majority of the basic processes were invented during the second half of the 19th century; since then, thousands of patents have been added which have improved the efficiency of the process or some part of the machinery used in the performance of the rolling operation (Schey, 1966).
Cold rolling process is one of the industrial practices employed in the manufacturing of plate, sheet, strip and foil products of aluminium and its alloys.
In spite of this very intensive activity, the problem of edge cracking which accompanies rolling process has not been completely resolved. Acceptable ways and means of preventing this defect is a challenge to commercial aluminium rolling operators.
REFERENCES
Agwandas A. K. (1988). Evaluation of local oils for cold rolling of aluminium sheets. Unpubished B. Eng. Degree Project, Ahmadu Bello University, Zaria, Nigeria.
Akshay G. P. and Ibrahim M. (2008). Mechanical properties of Zn-9%Al-3%Cu alloy after equal channel angular extrusion. Proceedings of the XIth International Congress and Exposition, Society for Experimental Mechanics Inc. Orlando, Florida USA, pp 1-7.
Atkins A. G. (1974). Hydrodynamic lubrication in cold rolling. International Journal of Mechanical Science, Pergamon Press, Great Britain, 16, 1-19.
Babaagba R. S. (1986). Evaluation of local oils as lubricants in deep drawing operations. Unpublished M.Sc. Thesis, Ahmadu Bello University, Zaria Nigeria.
Boldetti C., Pinna C. and Howard C. (2006). Measurement and prediction in plane strain compression tests of AA 5182. Journal of Material Science and Technology, 22(11), 1380-1386.
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