RR-A01-1003.1762540-1.pdf

This Research Report is issued under the fixed designation RR: A01-1003. You agree not to reproduce or circulate or quote, in whole or part, this document outside of ASTM International Committee/Society activities, or submit it to any other organization or standards body (whether national, international or other) except with the approval of the Chairman of the Committee having jurisdiction and the written authorization of the President of the Society. If you do not agree to these conditions, please immediately destroy all copies of this document. Copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. All rights reserved.

1 November 2013

Committee A01 on Steel, Stainless Steel and Related Alloys

Subcommittee A01.06 on Steel Forgings and Billets

Research Report: A01-1003

Interlaboratory Study to Establish Precision Statements for ASTM

A1038-13 Test Method for Portable Hardness Testing by the Ultrasonic

Contact Impedance Method Technical contact:

Gary Hayden, C P Industries 2214 Walnut Street Christy Park Plant MC KEESPORT, PA 15132 US [email protected]

ASTM International 100 Barr Harbor Drive

West Conshohocken, PA 19428-2959

RR: A01-1003

Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.

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1. Introduction:

Interlaboratory Study 619 was conducted to establish a precision statement for A1038, Test Method foroPortable Hardness Testing by the Ultrasonic Contact Impedance Method.

2. Test Method:

The Test Method used for this ILS is A1038-13. To obtain a copy of A1038, go to ASTMs website, www.astm.org, or contact ASTM Customer Service by phone at 610-832-9585 (8:30 a.m. - 4:30 p.m. Eastern U.S. Standard Time, Monday through Friday) or by email at [email protected].

3. Participating Laboratories: The following laboratories participated in this interlaboratory study: David L Ellis Co., Inc. Robert Ellis [email protected] Sun-Tec George Smolboski [email protected]

Wilson Instruments Nelson Bairos

[email protected]

4. Description of Samples:

There were 5 samples of varying targeted results used for this study. Each sample was supplied and prepared by King Tester Corporation. Test blocks were tested in a round style with all of the laboratories testing the same set of test blocks. Once one laboratory completed the testing, the blocks were shipped to the next laboratory on the schedule. Below is a list of the samples:

1. 0300142 Test Block 2. 0722420 Test Block 3. 0723157 Test Block 4. 0729385 Test Block 5. 0800213 Test Block

5. Interlaboratory Study Instructions Laboratory participants were emailed the test program instructions. For a copy of the instructions, please see Annex A.

6. Description of Equipment/Apparatus1:

For information on the equipment/apparatus used by each laboratory, please see Annex B.

1 The equipment listed was used to develop a precision statement for A1038-13. This listing is not an endorsement or certification by ASTM International.

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7. Data Report Forms:

Each laboratory was provided with a data report form for the collection of data. A copy of the data is provided in Annex C. Please note: The laboratories have been randomly coded and cannot be identified herein.

8. Statistical Data Summary:

A summary of the statistics calculated from the data returned by the participating laboratories is provided in Annex D.

9. Precision and Bias Statement:

Table 4 Comparative Vickers Hardness

Test Block

Calculated True

Hardness Valuei

ILS #388 Determined

Hardness Valueii

(Test Stand)

ILS #388 Determined

Hardness Valueiii

(Hand Held)

Bias (Test Stand)

Bias (Hand Held)

% %

0300142 143.06 NR NR NR NR

0729385 189.70 197.40 196.14 +4.06 +3.39 0800213 240.32 228.44 227.98 -4.94 -5.13 0722420 321.75 311.20 314.22 -3.28 -2.34 0723157 388.78 382.46 372.28 -1.63 -4.24

iThe average of the three testing laboratories calculated averages (obtained using an actual Vickers hardness tester) from ILS #619.

iiThe average of five testing laboratories calculated averages (obtained using UCI (ultrasonic contact impedence) hardness testing equipment with the data expressed in Vickers hardness numbers) from ILS #358. All included labs utilized 5kg test force.

iiiThe average of five testing laboratories calculated averages (obtained using UCI (ultrasonic contact impedence) hardness testing equipment with the data expressed in Vickers hardness numbers) from ILS #358. All included labs utilized 5kg test force.

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through the ASTM website (www.astm.org).

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Annex A: Procedure

10.1 Test ProcedureTo perform a hardness test, the probe is connected to the indicating unit and the instrument is turned on. The probe is held firmly (using a probe grip if needed) with its axis in a perpendicular position relative to the test piece surface. Hold the probe with both hands to achieve the best possible result. Carefully exert steady pressure against the test piece during the loading phase. Make sure that the vertical probe position is maintained as long as the load is effective. Some instruments indicate the end of the measurement by an acoustic signal and display the hardness value instantaneously. 10.2 AlignmentTo prevent errors from misalignment move the UCI probe with slow and steady speed. The probe should be perpendicular with respect to the surface. The maximum angular deviation from the perpendicular position should be less than 5 degrees. Avoid twisting of the probe housing. There should be no lateral forces on the indenter. Therefore, avoid slip. 10.3 Test DirectionHardness testing according to the UCI method generally can be carried out in any direction, without the necessity of corrections depending on the loading. There may be an effect of the measurement direction on the hardness measurement depending on the manufacturer and the test load of an UCI probe. This is due to the mass of the vibrating rod, which may influence the test load in dependence on the direction of measurement; that is, the mass of the rod will increase the load when measuring top to bottom and vice versa. This should be considered especially for test loads below 10 N. In this case the user has to verify the influence of test orientation on the hardness reading depending on test load and hardness of material. 10.4 Spacing IndentationAs per Test Method E384 the center distance between two adjacent indents in relation to the mean length of the diagonals must be (1) at least 3 times the amount for steel, copper and copper alloys, and (2) at least 6 times the amount for light metals, lead, tin and their alloys. If two neighboring indents vary in size then the mean indent diagonal of the larger indent must be used for calculation of the minimum distance. No point shall be measured more than once. 10.5 Reading of UCI InstrumentsHardness values can be read directly off the electronic display of the instrument. On some instruments, they can be displayed either as single figure showing the actual reading, or as average figure showing the average of the hardness readings taken so far. Equivalent hardness numbers on other scales can be obtained by using a hardness conversion table (see also Section 12) or by calibration according to Section 6. 10.6 Number of MeasurementsFive measurements taken in an area of approximately 650 mm2 shall constitute one test. If the material being tested is considered to be inhomogeneous, ten measurements or more shall be made to constitute one test. NOTE 1650 mm2 is an area approximately equal to 1 in.2. 10.7 ReportingThe numerical hardness value shall be followed by the symbol for the UCI test, HV(UCI) in the case of a Vickers reading with a suffix number denoting the test force in kgf. Example: 446 HV(UCI) 10 = UCI hardness number of 466 under a force of 10 kgf. If numerical hardness values are presented in other scales by calibration according to Section 6, they should analogously be reported as 45 HRC( UCI) or 220 HBW(UCI) etc. Reporting of converted values, see Section 12.

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Annex B: Apparatus

5.1 Instruments used for UCI hardness testing generally consist of (1) a probe containing a rod with a defined indenter, for example, a Vickers diamond, attached to the contacting end per Test Method E384 (see Fig. 1), (2) vibration generating means, (3) vibration detecting means, (4) electronic means for the numerical evaluation, and (5) a digital display, indicating the measured hardness number. 5.2 UCI ProbesThere are different probes available for UCI hardness testing. They typically cover static loads ranging from 1 N to 98 N. See also Appendix X1. They come also in different sizes with longer and shorter sensor rods for specials applications. And they are developed in two versions, that is, manually operated or equipped with a servo-motor for automatic testing. 5.3 Summary of Test MethodIn conventional workbench hardness testing like Brinell or Vickers testing according to Test Methods E10 and E384, the hardness value is determined optically by the size of the indentation in the material generated by a certain test load, after the indenter has been removed. In the mobile hardness test under applied load according to the UCI method, however, the size of the produced indents are not determined optically. Instead the contact area is derived from the electronically measured shift of an ultrasonic resonance frequency. To carry out the UCI test, a probe containing the rod with the indenter is excited into a longitudinal ultrasonic oscillation of about 70 kHz by piezoelectric ceramicsthe so-called zero frequency, which occurs when the indenter is vibrating in air.

5.3.1 A spring inside the probe applies the specified test load, the vibrating tip penetrates into the material creating an elastic contact, which results in a positive frequency shift of the resonating rod. This shift is related to the size of the indent area (contact area of the indenter with the material). The size, in turn, is a measure for the hardness of the test material at a given modulus of elasticity, for example, HV(UCI) according to Eq 1.

5.3.2 Therefore, the frequency shift is relatively small for hard materials, because the indenter penetrates not very deep into the test material leaving only a small indent. 5.3.3 The frequency shift becomes larger if the indenter penetrates deeper into the material, indicating medium hardness, in accordance with the larger test indentations. Analogously, the frequency shift becomes largest when soft materials are tested (see Fig. 2). 5.3.4 The instrument constantly monitors the resonance frequency, calculates the frequency shift when the specified test load has been reached either after the internal switch has triggered the corresponding measurement frequency in the case of handheld probes or after a specific dwell

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time has been elapsed in the case of motor driven probes. The instrument carries out the evaluation and calculations, and displays instantaneously the hardness value, for example, HV(UCI).

5.3.5 The frequency shift is a function of the indentation size of a defined indenter, for example, a Vickers diamond, at a given modulus of elasticity of the measurement system. 5.3.6 Eq 1 describes the basic relation in comparison to the definition of the Vickers hardness value: f = Frequency shift, A = indentation area, Eeff = effective elastic modulus (contains the elastic constants of both the indenter and the test piece), HV = Vickers hardness value, F = Force applied in the hardness test.

5.4 The Influence of the Elastic ConstantsAs can be seen in Eq 1, the frequency shift not only depends on the size of the contact area but also on the elastic moduli of the materials in contact. To allow for differences in Youngs modulus, the instrument has to be calibrated for different groups of materials. After calibration, the UCI method can be applied to all materials, which have the corresponding Youngs modulus.

5.4.1 As manufactured, the UCI instrument usually has been calibrated on non-alloyed and low-alloyed steel, that is, certified hardness reference blocks according to Test Method E384. Besides this, some instruments may be calibrated quickly, also at the test site, for metals such as high-alloyed steels, aluminum or titanium.

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Annex C:

Hardenss Measured on Vickers scale

Laboratory 1

Samples Replicates 1 2 3 4 5

0300142 Test Block 142.3 140.3 142.3 142.3 144.4 0722420 Test Block 328.5 321.4 325 324.9 325 0723157 Test Block 396.8 389.8 394.5 394.5 394.5 0729385 Test Block 194.2 194.2 190.9 189.4 191 0800213 Test Block 247.1 242.5 240.2 240.2 238

Samples Replicates 6 7 8

0300142 Test Block 144.4 142.3 143.3 0722420 Test Block 325 328.5 332.1 0723157 Test Block 389.8 399.3 394.5 0729385 Test Block 194.2 191 189.4 0800213 Test Block 240.2 240.2 244.8 Laboratory 2


0300142 Test Block 142.98 143.94 142.31 142.25 141.26 0722420 Test Block 321.01 315.05 325.98 321.39 318.57 0723157 Test Block 381.24 386.92 385.43 391.21 384.44 0729385 Test Block 191.48 187.29 188.39 189.24 191.65 0800213 Test Block 240.74 238.18 243.34 242.71 237.7


0300142 Test Block 143.2 142 142.91 0722420 Test Block 322.34 324.63 320.64 0723157 Test Block 384.68 387.42 392.74 0729385 Test Block 189.07 190.01 188.39

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0800213 Test Block 242.71 240.13 241.97 Laboratory 3


0300142 Test Block 143 144 143 146 142 0722420 Test Block 319 317 318 317 317 0723157 Test Block 388 385 386 382 386 0729385 Test Block 188 187 189 189 188 0800213 Test Block 242 240 239 235 238


0300142 Test Block 143 144 146 0722420 Test Block 320 316 318 0723157 Test Block 387 387 382 0729385 Test Block 187 189 186 0800213 Test Block 235 238 240

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Annex D:

Hardenss Measured on Vickers scale - h Values Critical value for h = 1.15 Lab 0300142

Test Block 0729385 Test Block

0800213 Test Block

0722420 Test Block

0723157 Test Block

1 -0.5098 1.0596 0.7724 1.0577 1.1424 2 -0.6424 -0.1325 0.3572 -0.1277 -0.4255 3 1.1522 -0.9272 -1.1295 -0.9300 -0.7169

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Hardenss Measured on Vickers scale - k Values Critical value for k = 1.47 Lab 0300142

Test Block 0729385 Test Block

0800213 Test Block

0722420 Test Block

0723157 Test Block

1 1.0813 1.2848 1.1709 1.1561 1.0237 2 0.6661 0.9354 0.8393 1.2069 1.1954 3 1.1777 0.6887 0.9616 0.4547 0.7233

i The average of the three testing laboratories calculated averages (obtained using an actual Vickers hardness tester) from ILS #619. ii The average of five testing laboratories calculated averages (obtained using UCI (ultrasonic contact impedence) hardness testing equipment with the data expressed in Vickers hardness numbers) from ILS #358. All included labs utilized 5kg test force. iii The average of five testing laboratories calculated averages (obtained using UCI (ultrasonic contact impedence) hardness testing equipment with the data expressed in Vickers hardness numbers) from ILS #358. All included labs utilized 5kg test force.

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