Hardness Test and Error Analysis of N80 Oil Casing Ding Feng 1, a, Zhi-min Li 2, b, Hong Zhang 3, c, Lei Shi, Wei Ma, Jian Yan

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1 Advanced Materials Research Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland Hardness Test and Error Analysis of N80 Oil Casing Ding Feng 1, a, Zhi-min Li 2, b, Hong Zhang 3, c, Lei Shi, Wei Ma, Jian Yan School of Mechanical Engineering, Yangtze University, Jingzhou Hubei , China a fengd0861@sina.com, b woshilzm@qq.com, c @qq.com Keywords: n80 oil casing; hardness test; error analysis Abstract: N80 oil casing is important equipment in petroleum drilling, to analyze the mechanical features of the N80 casing; we used Rockwell apparatus to test the hardness of N80 casing. And we have analyzed and eliminated the errors which may affect the result of the hardness test to ensure the reliability. At the same time, it summed up the causes of errors and the methods to avoid and reduce the errors during the Rockwell hardness test, and analyzed the hardness tester load, pressure head, the structure as well as the test sample roughness, shape and other factors which influenced the measurement results. Introduction Oil casing is mainly used for the support of the drilling and completion of the borehole wall, in order to ensure the normal operation of the wells in the conduct and completion of the drilling process. Due to the different geological conditions, underground complex stress state ask for relatively high quality of the casing itself [1]. Once the casing is damaged, it may lead to reduced production of the wells, or even scrapping. In this paper, a Rockwell hardness meter N80 oil casing hardness test is used as an indicator of the N80 casing mechanical performance of the mechanical properties of the N80 oil casing to inspect and analyze. The material partially against a hard object is pressed into its surface known as hardness. The hardness test is the simplest one in the material testing which can be estimated according to hardness. The hardness and other mechanical properties have a certain relationship, parts and other mechanical properties of the material. but due to the simplicity of the hardness test, during the test easily cause it the results have a greater change factors also will be changed, so it is very important for the study of the sources of error in the hardness test and for avoiding errors. In the Hardness test process of N80 oil casing, testers must carefully test results error analysis to ensure the reliability of the test results. Test Principle of Test N80 oil casing material, hard material, the smaller casing sample material wall thickness, taking into account the production of the specimen and the accuracy of the measurement results of the hardness test, in the test, we selected Rockwell hardness test N80 oil casing material sample to measure the hardness [2]. Rockwell hardness test principle is shown in Figure 1. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-12/05/16,08:59:55)

2 162 Materials, Transportation and Environmental Engineering Fig. 1 Schematic of the hardness test 1 Indentation depth in the initial test force F0; 2 Indentation depth under the total test force F0 + F1; 3 The depth of the elastic recovery after removal of the main test force F1; 4 Residual indentation depth; 5 The surface of the sample; 6 Measuring datum; 7 Indenter position; Rockwell hardness value is calculated as follows: Rockwell hardness=n-h/s (1) N-Constant, A, C, D, N, T-scale, N = 100; other ruler, N = 130; h-residual indentation depth, in units of mm; S-Constant, when the case of Rockwell hardness, S = 0.002mm. Specimen Preparation Taking into account the surface of the casing surface, the hardness test requires flat materials, and has some requirements on the surface roughness and surface cleanliness, it will test casing materials cutting and planing, grinding the series processing step, so as to achieve the requirements of the test [3]. Its size: 50mm 70mm 10mm. The Test Results The trials were carried out in the trial of the seven pilot sites testing the first material HRA ruler hardness tests to determine a more accurate scale choice. As measured hardness value 61.4HRA, the HRC ruler for more accurate detection. HRC ruler were detected in six points, test points without taking into account valid points to 5.The measured hardness values as shown in Table 1. Table 1. Rockwell hardness test results list Number of trials Unit Indenter material Initial test force Main test force Total test force Hardness values 1 HRA 120 Diamond cone HRC 120 Diamond cone HRC 120 Diamond cone HRC 120 Diamond cone HRC 120 Diamond cone HRC 120 Diamond cone Result average value 21.0

3 Advanced Materials Research Vols Error Analysis of the Hardness Test Sources of Error During the test of Hardness test on N80 casing, the source of the error of the Rockwell hardness test is summarized as follows: The impact of Pressure head on the measurement results: indenter test failed Rockwell hardness testing standards hardness block found hardness tester showing the value of the standard hardness block the nominal value of the larger error, error changes in the appearance of the size and pressure head and the actual measured standard hardness block hardness [4]. The impact of the load on the measurement results: the weight of the load bodies Rockwell hardness due to the use or improper storage rust its quality changes, leading to changes in load hardness tester system. When the actual value of the pre-load is greater than the nominal value, the main load caused by the plastic deformation of the indenter into the depth value becomes small, so that the hardness measurement results is greater than the actual value. The measurement results when the main load actual value is greater than the nominal value by the main load caused by the plastic deformation of the indenter is pressed into the depth becomes large, the hardness is lower than the actual value [5]. The impact of the rack and sample support on the measurement results: If the rack elastic deformation and aftereffect supporting institutions exist improperly adjusted or clean mismanagement, deformation and displacement, resulting in a false indentation depth and measured hardness values than the actual value of the low performance, which shows the value of a large degree of changes. The impact on the test sample measurement results: when testing different surface in Rockwell hardness measurement, the measurement results shown the different effects. Surface finish is lower, the greater the error in the measurement of the high hardness material. Surface parts hardness measurement error than the plane [6]. In addition, whether the measurement instructing means is accurate, or the test conditions to achieve the requirements of the test, the technical proficiency of the operator, and whether in strict accordance with the method steps of the test operation will have a certain influence on the measured values. Reduce the Error After analyzing Rockwell hardness test error sources, we propose the following measures to reduce experimental error: Do a good processing of the specimen before the test, the sample must be handled strictly in accordance with the requirements of the test. Keep the instrument in good working condition, in addition to time send metrological verification test of the department, in the day-to-day work to choose a better uniformity of standard hardness block showing the value of stability experiments, in order to timely identify problems and to maintain instruments in good working condition. Hire qualified testing personnel: laboratory personnel should be familiar with the works of the instrument, master the testing protocols, and operate in strict accordance with procedures. Between the hardness test sample s thickness and indentation, indentation distance to the edge of the sample must be in strict compliance with the provisions of the test standards or procedures: hardness measurement between the indentation to maintain the required distance requirements indentation the distance to the distance between the indentation to the edge of the sample is not less than 3 mm, the thickness of the sample is at least ten times the indentation depth. Hardness test loading speed test force of hold time should meet the test requirements. The Fixed results of curved specimen Rockwell hardness test measurement: the greater curvature of the curved surface hardness was measured using the Rockwell hardness test method, the measurement results need to be corrected, and the correction value can be checked on the

4 164 Materials, Transportation and Environmental Engineering "surface parts measured hardness correction table obtained. When measuring the hardness of the parts of this shape, a special table shall be especially designed, to make the table and the pressure head concentric. Analysis for Test After analysis by the source of error in the above hardness test for the N80 sleeve hardness test may generate the error conditions in the discussion, we got an understanding of the reliability of the test results. Specimen machining accuracy: during processing of specimen, by planing, milling and other processing methods for processing samples, the surface roughness of 0.8μm, found GB/T the requirements of the sample processing, so the error of the resulting is within the allowable range. The duration of the test force: the research report of the hardness testing of various materials have pointed out that the test force applied to have a greater impact on the material measured hardness value. In this experiment, the initial application time is 2S, the main test force application time is 3S, and is within the scope of the GB/T as indicated, so that the generated error is still within the allowed range, credible and reliable test results, in line with national standards. The error caused by the instrument itself: Because of the accuracy of the instrument itself and the use of custody incorrect manner, the error of the test measurement comes out, taking into account of this problem, the test instrument ruler hardness material before the measurement is performed on the specimen has been used, in order to make sure that the instrument is accurate and reliable, ruled out of this problem. Which can explain the results of the data obtained by the hardness test is credible. Summary By the hardness test we measured the N80 oil casing hardness of the material; After analyzing the sources of error that may exist on the hardness test are summarized, we proposed a way to avoid and reduce the error; After Investigation of the error on the measured hardness, we confirmed the test results are accurate and reliable; Display for the N80 oil casing material hardness test results showed the texture of the material sample uniform defect-free, good mechanical properties. taking into account of N80 oil casing work environment and the formation of N80 oil casing working state of high temperature and high pressure, corrosive, and continuous force, in these environments How would the N80 oil casing hardness change and whether it is able to achieve practical use to the desired requirements. Because of reduced Test conditions, the hardness changes of N80 oil casing material in complex condition have yet to be studied further. References: Reference an article: [1] Martyn Fear. Bit Technology and Bottomhole Assemblies, Society of Petroleum Engineers, Birmingham, England, JPT December (2011) [2] Stephan Hekelaar, Kenneth Gibson, Praful Desai, Smith Services, a Schlumberger Company, Increasing Reliability of Cutting/Pulling Casing in a Single Trip, Society of Petroleum Engineers, UK, SPE145494(2011)6-8. [3] Wen-xi He, Zhi-li Qi, Jian-hua Huo. Rockwell hardness test error analysis, (2008)3 [4] Kwabena Kwakwa, Data Governance the Next Step in Wellbore Stability, Energy Technology Assocs. Ltd, JPT OCTOBER (2002) [5] Wang Kai-yuan, Alteration of Testing Standards for 2009 Edition Rockwell Brinell and Vickers Hardness Test, Liaoning Dandong Wuyi Combustion Engine Part Co.Ltd, China, Foundry Technology,7(2011). [6] LI Xiao-dong, Influence Factors on Rockwell Hardness Test Results, Heilongjiang Provincial Station for Test and Checkup of Farm Machinery, China, Physical Testing and Chemical Analysis, 4(2010).

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