Quench Probe and Quench Factor Analysis of Aluminum Alloys in Distilled Water by Marco Fontecchio A Master’s Thesis Submitted to the Faculty of WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Master of Science in Materials Science and Engineering by ______________________________ May 2002 APPROVED: _____________________________________ Richard D. Sisson Jr., Advisor Professor of Mechanical Engineering Materials Science and Engineering Program Head ABSTRACT A 6061 aluminum probe was quenched with a CHTE probe-quenching system in distilled water while varying bath temperature and the level of agitation. Time vs. temperature data was collected during the quench by use of an ungrounded K-type thermocouple embedded inside the probe. Cooling rates and heat transfer coefficients, h, were calculated and Quench Factor Analysis (QFA) was also performed to quantitatively classify the quench severity. The data showed an increase in both maximum cooling rate and heat transfer coefficient and a decrease in the Quench Factor, Q, as bath temperature decreased and agitation level increased. Maximum heat transfer coefficient values ranged from 1000 W/m2K to 3900 W/m2K while maximum cooling rates of 50°C/s to 190°C/s were achieved. In addition, it was found that at higher levels of agitation, there was also an increase in the standard deviation of the cooling rate. i ACKNOWLEDGEMENTS This project could not have been completed without the guidance and direction from my advisor, Professor R.D. Sisson Jr. who aided from start to finish with advice on everything from test procedure to data analysis. He was also gave significant help in troubleshooting the test set-up. In addition, the constant hands-on help from Dr. Md. Manirumizzan was instrumental in facilitating the completion of the experimental testing and design of experimentation. And finally, I would like to thank Todd Billings, Steve Derosier, and Jim Johnston for their constant help in preparing my metallurgical test pieces. This project was funded by the Center for Heat Treating Excellence (CHTE) and could not have been completed without its financial assistance and desire for quenching data. In addition, I would like to thank the committee that selected me as the recipient of the Stoddard Fellowship for they made it financially possible for me to attend graduate school this past year. Without the help of the aforementioned people above, this research could not have been conducted and finished in a timely manner. For these reasons, a sincere thank you goes out to all of them. May 29, 2002 Marco Fontecchio ii LIST OF TABLES Page Table 2.1: Solutionizing Temperatures for Various Aluminum Alloys 6 Table 2.2: Soaking Time for Solution Heat Treating of 7 Wrought Aluminum Alloys Table 2.3: K-Constants for Various Aluminum Alloys 24 Table 3.1: Test Matrix for Quenching in Distilled Water 33 Table P1.1: Distilled Water Test Matrix 45 Table P1.2: Maximum Cooling Rates and Quench Factor Q as a 49 Function of Water Temperature and Agitation Level Table P1.3: Standard Deviation of Maximum Cooling Rate as 50 a Function of Agitation Level and Bath Temperatures Table P1.4: Ratio of Standard Deviation to Maximum Cooling Rate as 50 a Function of Agitation Level at Different Bath Temperatures Table P2.1: K-Constant Values for Quench Factor Analysis 60 Table P2.2: Distilled Water Test Matrix 62 Table P2.3: Variation in Quench Factor as a Function of Agitation and 70 Bath Temperature Table A.1: Comparison of AISI Carburized 8620 Metallurgical 83 Properties of and Oil and Polymer Quench Table A.2: Various Experimental Situations and Corresponding 86 Taguchi Experiment Size Table A.3: L9 Orthogonal Array for Experimental Testing 87 Table A.4: L9 Array with Results Column 88 Table A.5: ANOVA Table 90 Table A.6: Taguchi Design of Experimentation for Polymer Quenching 91 Table A.7: Taguchi Test Matrix for Polymer Quenching 92 iii LIST OF FIGURES Page Figure 2.1: Aluminum-Magnesium Phase Diagram 5 Figure 2.2: Typical Cooling Curve with Corresponding 9 Cooling Rate and Stages of Quenching Figure 2.3: Effect of Surface Finish on Heating and Cooling of an 12 Aluminum Cylinder Figure 2.4: Effect of Bath Temperature on Quench Rates 14 Figure 2.5: Differential Element of Size ∆x 15 Figure 2.6: Specific Heat as a Function of Temperature for Various 18 Aluminum Alloys Figure 2.7: Density Variation of 6061 Aluminum as a Function of 20 Temperature Figure 2.8: Thermal Conductivity of an Aluminum-Magnesium Alloy 20 as a Function of Temperature Figure 2.9: Cooling Curve and TTP Curve Analysis 26 Figure 2.10: Correlation of QFA to Hardness of As-Quenched 4130 Steel 27 Figure 3.1: Schematic of Complete Agitation System 29 Figure 3.2: CHTE Probe-Coupling Dimensions 31 Figure 3.3: Cross-Section of Probe-Coupling Interface with Alumina Seal 32 Figure P1.1: Cooling Curve and TTP Curve Analysis 43 Figure P1.2: CHTE Probe-Coupling Dimensions 44 Figure P1.3: Average Cooling Curves at Various Temperatures 47 for No Agitation Figure P1.4: Average Cooling Curves at Various Temperatures 47 at 880 rpm Figure P1.5: Average Cooling Curves at Various Temperatures 48 at 1850 rpm iv Figure P2.1: Typical Cooling Curve with Corresponding Cooling Rate 56 and Stages of Quenching Figure P2.2: Specific Heat as a Function of Temperature for Various 57 Aluminum Alloys Figure P2.3: Cooling Curve and TTP Curve Analysis 61 Figure P2.4: CHTE Probe-Coupling Dimensions 63 Figure P2.5: Schematic of CHTE Quench System 64 Figure P2.6: Effective Heat Transfer Coefficients for Various 67 Temperatures With No Agitation Figure P2.7: Effective Heat Transfer Coefficients for Various 68 Temperatures With An Agitation Level of 880 rpm Figure P2.8: Effective Heat Transfer Coefficients for Various 69 Temperatures With An Agitation Level of 1850 rpm Figure P2.9: Hyperbolic Regression of QFA as a Function of ‘h’ Max 70 Figure P2.10: Quench Factor As a Function of Maximum Heat 71 Transfer Coefficient Figure P2.11: Summation Region of Q as Seen on Heat Transfer 72 Coefficient Curves Figure A.1: Comparison of Old and New Polymer Cooling Curves 84 v TABLE OF CONTENTS Page 1.0 INTRODUCTION 1 1.1 Research Objective 1 1.2 Thesis Organization 2 2.0 LITERATURE REVIEW 4 2.1 Solution Heat Treating of Aluminum Alloys 4 2.2 Quenching 7 2.2.1 Stages of Quenching 8 2.2.2 Factors Affecting Quenching 10 2.2.2.1 Effect of Temperature 10 2.2.2.2 Effect of Agitation 11 2.2.2.3 Effect of Surface Finish 11 2.2.3 Aqueous Quenching Mediums 12 2.2.3.1 Water Quenching 13 2.3 Conductive Heat Transfer 15 2.3.1 Physical Properties of 6061 Aluminum 17 2.3.2 Heat Transfer Coefficient h 21 2.3.3 The Biot Number Bi 22 2.4 Quench Factor Analysis (QFA) 23 3.0 PROCEDURE 28 3.1 Experimental Set-Up 28 3.2 Sample Preparation 30 3.3 Conducting the Experiments 33 3.4 Test Matrix 33 3.5 Quench Factor Analysis Calculations 34 4.0 PUBLICATIONS 39 4.1 The Effect of Temperature and Agitation Level on the Quench 40 Severity of 6061 Aluminum in Distilled Water 4.2 Quench Factor Analysis and Heat Transfer Coefficient 53 Calculations for 6061 Aluminum Alloy Probes Quenched in Distilled Water 5.0 CONCLUSIONS 76 6.0 RECOMMENDATIONS AND FUTURE WORK 78 6.1 Modifications to CHTE Probe-Quench System 78 6.2 Polymer Quenchants 79 APPENDIX A: Polyalkylene Glycol (PAG) Quenching 81 APPENDIX B: Derivative Program 94 vi 1.0 INTRODUCTION Solution heat-treating of aluminum alloys allows the maximum concentration of a hardening solute to be dissolved into solution. This procedure is typically carried out by heating the alloy to a temperature at which one single, solid phase exists [1]. By doing so, the solute atoms that were originally part of a two phase solid solution dissolve into solution and create one single phase. Once the alloy has been heated to the recommended solutionizing temperature, it is quenched at a rapid rate such that the solute atoms do not have enough time to precipitate out of solution [2]. As a result of the quench, a saturated solution now exists between the solute and aluminum matrix. The cooling rate associated with the quench can be controlled through the variation of the quenching parameters such as bath temperature and degree of agitation. The variation of these parameters allows the heat treater the ability to increase or decrease the cooling rate to achieve certain mechanical properties as well as eliminate distortion and the possibility of cracking [3]. The cooling rate data can be quantitatively characterized by Quench Factor Analysis (QFA). QFA can classify the severity of a particular quench for a particular alloy by one value, Q. Generally speaking, the smaller the quench factor, Q, the higher the quench rate. Totten, Bates, and Mackenzie have done extensive work on the quench factor analysis of aluminum alloys and steel in hopes to prove the validity of QFA and its ability to classify a quench (i.e. the quench conditions and alloy being quenched) [4-9]. 1.1 Goals and Objectives The primary goal of this thesis is to experimentally determine the effect that quenching parameters have on the quench severity of 6061 aluminum probes in distilled 1 water. The parameters of interest include: initial bath temperature and agitation rate. The effects of these parameters will be quantified through the calculation of cooling rates, heat transfer coefficients, and Quench Factor Anaysis.. 1.2 Thesis Organization The thesis is divided into six chapters. Chapter 1 is an introduction that provides an overview of the research within and why is it important. Chapter 2 is a thorough review of relevant literature and previous work completed by others in the field of heat treating and quenching. The literature review focuses on the key aspects of the stages of quenching as well as a mathematical analysis called Quench Factor Analysis, which can classify the severity of a quench for the alloy being quenched. These research topics allowed for an understanding of the project at hand. Chapter 3 details the experimental set-up and testing procedures along with a test matrix that laid out the experiments to be conducted. Chapter 3 also describes the equipment used as well as sample preparation and methods for analyzing the collected data. Chapter 4 presents a series of two papers that were written and submitted to journals. The first paper entitled, “The Effect of Temperature and Agitation Level on the Quench Severity of 6061 Aluminum in Distilled Water”, written by M. Fontecchio, M. Maniruzzaman, and R.D. Sisson, Jr. describes the effect of quenching parameters through quenching 6061 aluminum in distilled water. This article was submitted to the American Society of Metals’ (ASM) 13th Annual International Federation for Heat Treatment & Surface Engineering (IFHTSE) Congress. The second article, entitled, “Quench Factor Analysis and Heat Transfer Coefficient Calculation for 6061 Aluminum Alloy Probed Quenched in Distilled Water”, written by M. Fontecchio, M. Maniruzzaman, and R.D. Sisson, Jr. presents a comparison of QFA 2 and heat transfer coefficients calculations in 6061 aluminum probes. This paper will be submitted to the “Journal of Materials Processing Technology”. Chapter 5 is a compilation of conclusions that were drawn, not only in the published papers, but from all research and experimentation conducted in this thesis. The final chapter, Chapter 6, explains how the work could be improved through recommendations on equipment used as well as expanded through the use of polymer quenchants and different alloy types. 3