Hardness Testing of Metals Proficiency Testing Program Round 8

Size: px

Start display at page:

Download "Hardness Testing of Metals Proficiency Testing Program Round 8"

May Horton
6 years ago
Views:

1 REPORT NO. 916 Hardness Testing of Metals Proficiency Testing Program Round 8 June 2015 ACKNOWLEDGMENTS PTA wishes to gratefully acknowledge the technical assistance provided for this program by Mr G Pownall, ARL Laboratory Services Pty Ltd. Also our thanks go to ARL Laboratory Services Pty Ltd, for the supply and homogeneity testing of the samples. COPYRIGHT PROFICIENCY TESTING AUSTRALIA 2015 PO Box 7507 Silverwater NSW 2128 AUSTRALIA

2 CONTENTS 1. FOREWORD 1 2. FEATURES OF THE PROGRAM 1 3. FORMAT OF THE APPENDICES 2 4. STATISTICAL DESIGN OF THE PROGRAM 2 5. OUTLIER RESULTS 2 Table A: Summary Statistics for All Tests 3 Table B: Summary of Statistical Outliers 4 6. PTA AND TECHNICAL ADVISER'S COMMENTS 4 7. REFERENCES 7 APPENDICES APPENDIX A Summary of Results Brinell Hardness A1.1 Vickers Hardness A2.1 Rockwell B Hardness A3.1 Methods Used and Surface Preparation A4.1 APPENDIX B Homogeneity Testing B1.1 APPENDIX C Instructions to Participants C1.1 Results Sheet C2.1

3 -1-1. FOREWORD This report summarises the results of a proficiency testing program on the hardness properties of metals. It constitutes the eighth round of an ongoing series of programs. Proficiency Testing Australia (PTA) conducted the testing program in May The aim of the program was to assess laboratories' ability to competently perform the nominated tests. The Program Coordinator was Dr M Bunt. The Technical Adviser was Mr G Pownall, ARL Laboratory Services Pty Ltd. This report was authorised by Mrs F Watton, PTA Quality Business Development Manager. 2. FEATURES OF THE PROGRAM (a) A total of 14 laboratories participated in the program, all of which returned results for inclusion in the final report. Laboratories from the following countries received samples: 11 AUSTRALIA 1 HONG KONG 1 MALAYSIA 1 SAUDI ARABIA To ensure confidential treatment of results, each laboratory was allocated a unique random code number. Reference to each laboratory in this report is by its code number. (b) The results reported by participants are presented in Appendix A. (c) (d) (e) Each laboratory was provided with a steel sample, approximately 60 mm in diameter and 30 mm thick. The sample was to be tested for Brinell, Vickers and Rockwell B hardness testing. Laboratories were requested to perform the tests according to the Instructions to Participants provided and to record the results, along with an estimate of their measurement uncertainty (MU) for each result, on the accompanying Results Sheet, which was distributed with the samples. Copies of these documents appear in Appendix C. Prior to distribution, the samples were tested for homogeneity by ARL Laboratory Services Pty Ltd. Based on the results of this testing, the homogeneity of the samples was established (see Appendix B).

4 -2-3. FORMAT OF THE APPENDICES (a) Appendix A is divided into four sections (A1-A4). Sections A1-A3 contain the analysis of results reported by laboratories for Brinell, Vickers and Rockwell B hardness. These sections contain: i) a table of results reported by laboratories for each test, with estimates of their MUs and calculated z-scores; ii) a listing of the summary statistics; and iii) ordered z-score charts. Section A4 contains information on the methods used by the participants and the surface preparations they performed. (b) (c) Appendix B contains details of the homogeneity testing. Appendix C contains copies of the Instructions to Participants and Results Sheet. 4. STATISTICAL DESIGN OF THE PROGRAM For each statistically analysed test, robust statistical procedures were used to generate the z-scores and summary statistics for each hardness determination - number of results, median, normalised interquartile range (IQR), uncertainty of the median, robust coefficient of variation (CV), minimum, maximum and range. For each participant, the robust z-score calculated for each hardness result was based on the average hardness value reported for each test. 5. OUTLIER RESULTS Robust z-scores have been used to assess each laboratory s testing performance. When calculated from single results, z-scores are used to detect excessively high or excessively low results in comparison to the consensus value (the median). Any result with an absolute z-score greater than or equal to 3.0 (i.e or 3.0) is classified as an outlier. For further details on the calculation and interpretation of robust z-scores, please see reference [1].

5 -3- The following table summarises the results submitted by participants for the program. Table A: Summary Statistics for All Tests Test Summary Statistics Average Result Brinell Hardness (HBW) Vickers Hardness (HV) Rockwell B Hardness (HRB) Number of Results 12 Median Normalised IQR 1.7 Uncertainty (Median) 0.6 Number of Results 12 Median Normalised IQR 7.7 Uncertainty (Median) 2.8 Number of Results 13 Median Normalised IQR 1.51 Uncertainty (Median) 0.52 Notes: 1. For each test, the results for all test methods were pooled for analysis. 2. Summary statistics were calculated for the average hardness value reported for each test. normiqr 3. The uncertainty of the median was calculated as:. 2 n

6 -4- Table B: Summary of Statistical Outliers (By laboratory code number) Test Outliers (Laboratory Code No.) Brinell Hardness 14 Vickers Hardness - Rockwell B Hardness - 6. PTA AND TECHNICAL ADVISER S COMMENTS Consensus values (medians), derived from participants results, are used as the assigned values in this program. These values are not metrologically traceable to an external reference. The summary statistics, uncertainties of the assigned values and outliers, for each of the tests, are reported in Tables A and B above. Complete details of the statistical analyses appear in Appendix A. 6.1 Return rate All of the 14 laboratories that participated in the program returned results. Of these 14 laboratories, 11 (79%) submitted results for all three tests. The return rate for all tests is as follows: Brinell Hardness 12 out of 14 86% Vickers Hardness 12 out of 14 86% Rockwell B Hardness 13 out of 14 93% 6.2 Performance summary One or more statistical outliers were reported by one of the 14 laboratories (7%) that returned results in this round of the program. For comparison, none of the participants reported outlier results in Round 7 of this program (see Report No. 891 for more details). A total of 37 results were analysed in this program. Of these results, one (3%) was an outlier result.

7 Brinell Hardness A total of 12 laboratories tested the sample for Brinell hardness. Of these laboratories, seven tested using the AS 1816 method. Two laboratories tested using the ISO 6506 method. Two laboratories tested using the ASTM E10 method. One laboratory did not specify their method of testing (see Appendix A4 for more details). For all methods pooled, the median and standard error of the Brinell hardness results was ± 0.6 HBW. The methods were pooled when analysing the results. The CV for the Brinell hardness results for this round was 0.9%. This is lower than the CV of 1.6%, obtained for the Brinell hardness results in Round 7 of this program (see Report No. 891). One laboratory (code 14) reported an outlier result for Brinell hardness. One laboratory (code 1) obtained an absolute z-score between 2.0 and 3.0. The Brinell test involves first measuring the diameter of the impression then converting that diameter to obtain the final HBW number. It is possible that laboratory 14 mistakenly reported the raw diameter, instead of the HBW number, or made an error in their conversion. Nine laboratories reported measurement uncertainties associated with their Brinell hardness test results in this round. 6.4 Vickers Hardness Of the 12 laboratories that tested the sample for Vickers hardness, eight tested using the AS 1817 method. One laboratory tested using the ISO 6507 method. Two laboratories tested using the ASTM E384 method. One laboratory did not specify their method of testing (see Appendix A4 for more details). For all methods pooled, the median and standard error of the Vickers hardness results was ± 2.8 HV. The methods were pooled when analysing the results. The CV for the Vickers hardness results for this round was 4.2%. This is higher than the CV of 3.2%, obtained for the Vickers hardness results in Round 7 of this program (see Report No. 891).

8 -6- There were no outliers reported for Vickers hardness. Nine laboratories reported measurement uncertainties associated with their Vickers hardness test results in this round. 6.5 Rockwell B Hardness A total of 13 laboratories tested the sample for Rockwell B hardness. Of these laboratories, eight tested using the AS 1815 method. One laboratory tested using the ISO 6508 method. One laboratory used both AS 1815 and ISO Two laboratories tested using the ASTM E18 method. One laboratory did not specify their method of testing (see Appendix A4 for more details). For all methods pooled, the median and standard error of the Rockwell B hardness results was ± 0.52 HRB. The methods were pooled when analysing the results. The last round of the Hardness Testing of Metals program in which the participants tested a sample for Rockwell B hardness was Round 6. The CV for the Rockwell B hardness results for this round was 1.7%. This is higher than the CV of 1.0%, obtained for the sample tested for Rockwell B hardness in Round 6 of this program (see Report No. 870). There were no outliers reported for Rockwell B hardness. Ten laboratories reported measurement uncertainties associated with their Rockwell B hardness test results in this round.

9 -7-7. REFERENCES 1. Guide to Proficiency Testing Australia (2014). (This document is located on the PTA website at under Programs / Documents). 2. AS : 2007 Metallic materials Rockwell hardness test Test method (scales A, B, C, D, E, F, G, H, K, N, T). 3. AS : 2007 Metallic materials Brinell hardness test Test method (ISO : 2005, MOD). 4. AS : 2003 Metallic materials Vickers hardness test Test method (ISO : 1997, MOD). 5. ISO : 2014 Metallic materials Brinell hardness test Part 1: Test method. 6. ISO : 2005 Metallic materials Vickers hardness test Part 1: Test method. 7. ISO : 2015 Metallic materials Rockwell hardness test Part 1: Test method. 8. ASTM E10 Standard Test Method for Brinell Hardness of Metallic Materials. 9. ASTM E18 Standard Test Methods for Rockwell Hardness of Metallic Materials. 10. ASTM E384 Standard Test Method for Knoop and Vickers Hardness of Materials.

10 APPENDIX A Summary of Results

11 Section A1 Brinell Hardness

12 A1.1 Lab Code Temp. ( o C) Brinell Hardness (HBW) Results and Z-Scores Test 1 Test 2 Test 3 Average MU (±) Z-Score % % % Summary Statistics Statistic Average Result Number of Results 12 Median Normalised IQR 1.7 Uncertainty (Median) 0.6 Robust CV 0.9% Minimum 176 Maximum 204 Range 28 Note: 1. Summary statistics and z-scores have been calculated for the average results reported.

13 6 Robust Z-Score A1.2 3 Brinell Hardness (HBW) Laboratory Code

14 Section A2 Vickers Hardness

15 A2.1 Vickers Hardness (HV) Results and Z-Scores Lab Code Load Temp. ( o C) Test 1 Test 2 Test 3 Average MU (±) Z-Score 1 HV HV HV HV HV HV % HV HV HV % HV HV % HV % 0.19 Summary Statistics Statistic Average Result Number of Results 12 Median Normalised IQR 7.7 Uncertainty (Median) 2.8 Robust CV 4.2% Minimum 174 Maximum 188 Range 14 Note: 1. Summary statistics and z-scores have been calculated for the average results reported.

16 Robust Z-Score A2.2 3 Vickers Hardness (HV) Laboratory Code

17 Section A3 Rockwell B Hardness

18 A3.1 Lab Code Temp. ( o C) Rockwell B Hardness (HRB) Results and Z-Scores Test 1 Test 2 Test 3 Average MU (±) Z-Score % % 0.60 Summary Statistics Statistic Average Result Number of Results 13 Median Normalised IQR 1.51 Uncertainty (Median) 0.52 Robust CV 1.7% Minimum 85.8 Maximum 89.3 Range 3.5 Note: 1. Summary statistics and z-scores have been calculated for the average results reported.

19 Robust Z-Score A3.2 3 Rockwell B Hardness (HRB) Laboratory Code

20 Section A4 Methods Used and Surface Preparation

21 A4.1 Methods Used Lab Code Brinell Hardness Vickers Hardness Rockwell B Hardness 1 AS AS AS AS AS AS ASTM E ASTM E10 ASTM E384 ASTM E18 6 BS EN ISO 6506 Part 1: 1999 BS EN ISO 6507 Part 1: 1998 BS EN ISO : AS Sect 7 - AS Sect 7 8 ISO AS AS AS , ISO ASTM E10-07 AS ASTM E18 11 AS AS AS AS AS AS AS 1816 AS 1817 AS 1815

22 A4.2 Surface Preparation Lab Code Preparation Details 1 Side painted yellow was ground to grit 240 prior to testing. The hardness was checked at quarter radius. 2 Paint removal with belt sander - P120 paper. Light sanding with P200 sand paper. Orbital polisher - 2 cycles on piano pad, 1 cycle on allegro pad, 4 cycles on plus pad. 3 Snow ground yellow surface. Vickers ground to P Milling surface grinding polish with 240-grit sand paper. 5 Finish grinding fine polishing. 6 No surface preparation. 7 Surface ground of tested face (yellow). Normal machining of obverse side (blue). 8 Yellow surface was machined - milling, surface ground and hand polished to P1200 grit (as per AS ). Blue surface (opposite) was machined - milling, surface ground to ensure both surfaces were flat and parallel. 9 Steel sample was prepped with 320 grit paper to obtain a smooth surface for testing. 10 Both faces surface ground. Test face polish to 400 grit wet/dry disks. 11 Hand polished to 2000 grit. 12 Surface preparation performed but no details given. 13 Test block machined on both faces to ensure flatness and smoothness. Test surface finished to 3µm diamond smoothness. 14 Surface preparation performed but no details given.

23 APPENDIX B Homogeneity Testing

24 B1.1 HOMOGENEITY TESTING Before the samples were distributed to participants, eight randomly selected samples were tested for homogeneity by ARL Laboratory Services Pty Ltd. The results of the homogeneity testing are displayed below: Homogeneity Testing Results Brinell HBW 10/3000 Sample No. Test 1 Test 2 Test 3 Average Vickers HV 10 Sample No. Test 1 Test 2 Test 3 Average

25 B1.2 Rockwell HRB Sample No. Test 1 Test 2 Test 3 Average Analysis of the homogeneity testing data indicated that the samples were sufficiently homogeneous for the program and, therefore, any participant results identified as outliers cannot be attributed to sample variability.

26 APPENDIX C Instructions to Participants and Results Sheet

27 C1.1 PROFICIENCY TESTING AUSTRALIA Hardness Testing Of Metals Proficiency Testing Program Round 8, May 2015 Instructions to Participants To ensure that the results of this program can be analysed correctly, participants are asked to adhere carefully to these instructions. 1) The sample for this hardness testing program consists of a steel sample, approximately 60mm in diameter and 30mm thick. The sample has been painted blue on one side and yellow on the other side, and has a number labelled on the circumference. 2) The sample is to be tested for Brinell, Vickers and Rockwell B hardness. Participants may wish to improve the surface to provide a better testing surface. The side painted yellow is the side that should be prepared and tested. 3) The sample should be treated as a routine laboratory sample. All testing, recording and reporting is to be performed in accordance with your routine test methods. 4) Please use the attached result sheet to record and report your results to Proficiency Testing Australia. Please also report the method used for testing (e.g. AS , ISO , etc. for Brinell hardness testing, AS , ISO , etc. for Vickers hardness testing, AS , ISO , etc. for Rockwell HRB hardness testing). 5) Do not discard the hardness test sample until you have received the final report. You may be asked to carry out a retest or to return the sample to Proficiency Testing Australia for retesting at the laboratory that performed the homogeneity tests. 6) For this program, your laboratory has been allocated the code number on the attached Results Sheet. All reference to your laboratory in reports associated with this program will be via this code number, thus ensuring the confidentiality of your results. 7) Laboratories are also requested to calculate and report an estimate of uncertainty of measurement for each reported measurement result. All estimates of uncertainty of measurement must be given as a 95% confidence interval (coverage factor k 2). 8) Return the Results Sheet, either by mail, or facsimile, to: Mark Bunt Proficiency Testing Australia PO Box 7507 Silverwater NSW 2128 AUSTRALIA Telephone: ( ) Fax: mbunt@pta.asn.au All results should arrive at the above address by no later than Thursday 21 May Results reported later than this date may not be analysed in the final report. Hardness Testing of Metals, Round 8 May 2015 Page 1 of 2

28 C2.1 PROFICIENCY TESTING AUSTRALIA Hardness Testing Of Metals Proficiency Testing Program Round 8, May 2015 RESULTS SHEET Laboratory Code: Sample I.D. Scale Report to nearest Test Temp ºC Results Test 1 Test 2 Test 3 Average MU (±) Standard (AS, ISO, etc.) Brinell ( / / ) (mm/kg/s) 1 BHN HV ( ) Insert load used 1 HV HRB 0.1 HRB Did you carry out surface preparation on the obverse surfaces of the samples for the hardness tests? Yes / No If Yes, please give details of preparation Print Name: Signature: Date: Hardness Testing of Metals, Round 8 May 2015 Page 2 of 2

29 -----End of Report-----

Report No Air & Emissions Proficiency Testing Program. Round 9. Particulate Matter on Filter Paper. March 2017

Report No Air & Emissions Proficiency Testing Program. Round 9. Particulate Matter on Filter Paper. March 2017 Report No. 1016 Air & Emissions Proficiency Testing Program Round 9 Particulate Matter on Filter Paper March 2017 Acknowledgments PTA wishes to gratefully acknowledge the technical assistance provided