Portable Hardness Testing Using Leeb and Portable
Contents
1. deep or more Equotip Application Booklet 27 2015 Proceq SA Question Specification Equotip Bambino 2 Equotip Piccolo 2 Equotip 550 Leeb Equotip 550 Portable Rockwell Question 4 Hardness scale and re quired range of hardness Question 5 Material type s Question 6 Surface roughness Question 7 Part geometry What scale is re quired by customer for reporting and what is high end What material is the customer testing Is the surface rougher than 3 2 um 124 inch ISO N8 Ra Is surface preparation required Outside radius of curvature less than 10 mm 0 400 Outside radius of curvature greater than 10 mm 0 400 Inside radius of curvature less than 11 mm 0 433 Inside radius of cur vature greater than 11 mm 0 433 Inside sphere of curvature less than 11 mm 0 433 Inside sphere of curvature greater than 11 mm 0 433 Outside sphere of curvature less than 10 mm 0 400 Outside sphere of curvature greater than 10 mm 0 400 Additional notes Product choice limited impact devices data sheet for possibili 7OHRC max ties of hardness scale conversions from HL converts to com mon scales dependent on material See data sheet See data sheet for other scales Reference impact devices and Equotip 550 Portable Rockwell for metals only data sheet for possibilities in combination with hardness scale conversions Yes re2. Figure 13 Usage of standard support rings on curved surfaces Equotip Application Booklet 22 2015 Proceq SA Testing on Cylindrical Test Surfaces e g Boilers and Pipes Cylindrical test objects can be tested with the support rings Z10 15 R 10 to 15 mm cylinder radius Z14 5 30 R 14 5 to 30 mm and 225 50 R 25 to 50 mm cylinder radius The support rings HZ11 13 HZ12 5 17 and HZ16 5 30 are well suited for Leeb hardness measurements on hollow cylindrical surfaces such as the inside of pipes and boilers of R 11 to 13 Figure 14 Support rings Z10 15 mm R 12 5 to 17 mm and R 16 5 to 30 mm cylinder radii respectively Z14 5 30 and 225 50 For convenience particularly when used with Proceq s advanced Leeb im pact devices these support rings can be rotated by 360 around the longitu I gt Zz dinal axis of the impact device By means of a grub screw the usercanfree __ fe as ly align the rectangular support ring to match the orientation of the impact device handle and to find the optimal position with respect to the sample Sein ad Figure 15 Support rings HZ11 13 and HZ12 5 17 Testing on Spherical Test Surfaces For spherical test situations Proceg offers the support rings K10 15 R 10 Y to 15 mm spherical radius and K14 5 30 R 14 5 to 30 mm spherical ra dius Accordingly hollow spherical surfaces can be tested with the support rings HK11 13 R 11 to 13 mm spherical radius
3. HK12 5 17 R 12 5to17 _ mm spherical radius and HK16 5 30 R 16 5 to 30 mm spherical radius FI94re 16 Support ting 10 15 The support rings for spherical test requirements are symmetrical around the guide tube eliminating the need of alignment of the support ring Figure 17 Support ring HK16 5 30 and HK11 13 Testing in Recesses For hardness tests inside recesses such as the bases between the teeth of Q gears the support rings of the above mentioned impact devices do not fit For these situations Proceq offers the DL long tip system This is a special impact body and support ring combination which can reach into many such recesses Figure 18 DL support ring and DL impact body Universal Support Ring The most versatile support ring is called UN This ring embraces the need to test even more complex geometries Examples can be seen below n A Cun ma tls 4 T Figure 19 Examples for usage of UN support ring Figure 20 Support ring UN If none of these solutions apply to your sample geometry please contact your local Proceq representative Equotip Application Booklet 23 2015 Proceq SA 5 7 Combined Equotip Leeb and Portable Rockwell Measuring Methods Hardness testing is not always as straightforward for exotic materials where desirable hardness conver sions are not available or when dealing with non ideal samples due to lack of mass thickness and other critical geometries Although there i
4. be found in chapter 2 3 Mass and Wall Thickness Limitations This method is specially suited for coarse grained parts as well as forgings and cast materials with a cer tain thickness and mass More details about the requirements can be taken from the Operating Instruc tions of the instrument Equotip Application Booklet 12 2015 Proceq SA 4 2 Portable Rockwell Method The Portable Rockwell metal hardness tes ter is based as its name suggests on the static Rockwell measuring principle where l 2 i the penetration depths under a defined 3 preload are measured before and after ap h plication of a large force i d Preload Total Load Preload During measurements with the Portable Rockwell probe a diamond indenter is forced into the test piece to be measured and then released back out of the material The indentation depth of the diamond is continuously measured while the load is applied and released From the indentation depths d and d recorded at two defined loads the difference is calculated A d d The difference A reflects the plastic deformation and therefore is a direct measure of the hardness of the material The Portable Rockwell method covers a wide range of applications like hardness measurements on small light thin walled or tubular test objects but also large and heavy objects can be tested as long as the surface roughness and grain size are small enough Figure 5 Portable Ro
5. goal of materials testing is to quantitatively characterize those properties of the different materials by the means of specific parameters and concrete numerical quantity values Because of the comparatively quick and easy execution of a hardness test this is still the most used method in order to get some information about the mechanical properties of the material However before going into more detail about what hardness is and how it can be measured a step by step guide will help the user to find the best suited tool for the specific application and highlight what has to be considered to get reliable results Oil and Gas Automotive Figure 1 Typical industries for which measuring hardness is of high importance Equotip Application Booklet 3 2015 Proceq SA 2 From Specific Application to Reliable Hardness Values 2 1 Method Selection Choosing the appropriate portable method depends on the task Selection is often based on controlling the indentation size and overcoming certain mass limitations of the method The decision regarding which tester and method to use must be determined by analysing the application in its entirety Each of the major variables present in the examination has to be evaluated and it has to be determined which portable hardness testing instrument and method are least affected In addition requirements for electronic documentation and the permanence of any indentation on the test surface are also factors t
6. of the reference value Portable Rockwell Method A simple test should be performed on the test equipment according to DIN 50157 1 Annex D each day before the start of testing and after testing In this indirect check measurements are performed on certi fied hardness reference blocks in the corresponding hardness range The test consists of at least three indentations on a hardness reference block in accordance with DIN 50157 in the range of 20 HRC to 70 HRC The average value should be determined from these three readings The test equipment can be considered to be satisfactory if the difference between the average of the hardness value read off and the hardness of the hardness reference block are less than or equal to the tolerance limit of 3 HRC If not the instrument should not be used and a complete indirect test should be performed in accordance with DIN 50157 2 2 5 Execution of Measurements The test shall be performed perpendicular to the test surface i e at an angle of 90 Deviations of gt 5 from the right angle to the test surface will result in errors which cannot be neglected and are therefore unallowable For uneven surfaces support rings are available for Leeb and Portable Rockwell testers to provide a stable position of the impact device An overview can be found in chapter 5 6 Using Equotip Leeb Support Rings Vibrations or movements of the specimen and or the probe during the hardness test can affect the result an
7. particularly suited for scratch sensitive polished or thin parts as well as for profiles and pipes The automatic combination of measurement methods extends the scope of the Equotip 550 to a large area of use And Equotip 550 is a future proof investment as It can be extended with additional test methods and features currently in development Because of this the Equotip 550 is the hardness testing instrument that offers you the maximum flexibility of portable hardness testing applications Just one instrument platform offers several portable hardness testing methods With this flexibility you will be able to cover additional applications in the future by just adding the corresponding probe The new Equotip 550 platform covers all the advantages of the two dif ferent test methods and thus offers reliable tailor made solutions to nearly all mobile hardness testing problems 4 4 Standardization for Portable Hardness Testing Although portable hardness testing has been applied in the practical field for several decades there has always been a lack of standardization for the specific physical test methods Most commonly portable equipment was used and the test results compared with the hardness values obtained with conventional bench top hardness testers like Vickers Brinell or Rockwell machines By doing this the specific prop erties and the limitations of the portable hardness testing equipment were not noticed appropriately re sulting in poten
8. splash electronics Electronics may be kept a dis ing will damage electronics tance from impact device with increased likelihood of remaining clean and dry Test location OK refer to drawing for dimensions accessibility housing may get in the way Most flexible all Device separated impact devices from the Touch separated from screen Unit via 2 Touchscreen Unit m cable Optional and are possible longer cables avail to be used Can able extend cable length to 16 feet 5 m for remote testing Im pact device DL and DC can access very tight spaces Direct to PDF and No Yes Yes USB stick Internal saving of Yes Yes Yes test results Internal data 2 000 Up to 1 000 000 Up to 1 000 000 Capacity Yes Yes ID type simple se No Yes download only quential or advance custom alpha nu meric Test results documenta tion Download to PC Sequential Custom amp Custom amp extensive alpha extensive alpha numeric numeric Direct to printer PDF to print PDF to print Operator ID No Test results maintenance amp repair Capable of simple repair by user es es Yes Replace support rings Replace impact body Yes Replace cable Replace impact Replace batteries External charger Good for produc tion testing Firmware upgrades Yes free via Yes free via Yes free via Yes free via internet internet internet internet No No No No No No Yes Yes Yes NA No No No Yes No
9. standard In order to recognize systematic deviations reference specimens are needed Typically these are calibrated hardness reference blocks of specified size thickness and hardness The absolute accuracy of the equipment can be controlled using the Verification Wizard of the Equotip 550 instrument and it is recommended to carry out this verification once a day or each shift b Repeatability Random Errors or Precision Random influences e g mechanical friction electronic noise ambient conditions lead to random errors of the measuring instrument The measured values vary or scatter even when correctly calibrated hardness testers are used for measurements on an ideal test object with perfect surface roughness and homogeneity of surface hardness These errors cannot be corrected because they occur by chance i e in different directions and siz es The smaller the variation or scattering the better the repeatability The repeatability precision is a Characteristic of the instrument and typically is below 1 with hardness testers The absolute accuracy and the repeatability of the equipment can be controlled using the Verification Wizard of the Equotip 550 instrument and it is recommended to carry out this verification once a day or each shift c Subjective Influence by the User or Reproducibility The user also represents a potential source of error Different handling of the instrument may occa sionally lead t
10. test piece a magnet contained within generates a voltage in a coil system that encircles the guide tube Typically a tungsten carbide or ipachohace diamond ball indenter located on the end of the impact Rebound phase gt body strikes the material causing the impact body to re bound from the surface at a slower velocity The softer the material the bigger the indentation causing a larger loss of energy and a slower rebound speed which in turn produces a proportionally lower voltage as the magnet returns through the coil The hard ness value HL is calculated from the ratio of the impact and rebound speed The third letter in the Leeb Hardness unit indicates the impact device used D for impact device D etc This value can then be con verted by the software to display conventional HRC HV or HB scales along with others Time ___ gt At the time this tester was considered to be revolutionary When used in the appropriate application these devices are quite accurate very simple to use and the repeatability is high The most critical variables affecting the test are part thickness and mass As described above there is an impact body that is released at a given velocity onto the surface of the object under test If the mate rial thickness is too thin with little mass then the material actually flexes on impact This influences the rebound velocity and in turn affects the reading obtained Details can
11. with the finest grit Each grinding step is done perpendicu lar to the previous one Each grinding step is not finished until all of the marks from the previous step have been ground away The individual grinding steps should be performed with light pressure on the machine There is no defined relationship between the grit of the grind ing medium and the achievable surface roughness R The maximum allowable surface roughness depends on the test method used and the force applied Detailed data regarding the desired or acceptable surface roughness values can be taken from Table 2 Roughness requirements To deter mine the actual roughness on the test object the Surface Roughness Comparator Plate shipped with the Equotip 550 helps to estimate POPP Hee EEE EEE EEE EHTEL E EEE EEE EEE EEE EEEE EEE E EEO E EEE E EEE EE EEEE EE EEE TE EEE EEE EEEEEEEE EE OSE EEO SE EE EEEOEEEEEE HELE EE ESEEE ESET E SHEE ESEEHE EEE EEE EEEEE EOE EEEEEETEEEEEEEEETETEEEEEE EEE EEEEEE EERE EEEEEH ELE EEEEEEEH ELE ESSE EEE HELE EDEL ESE EELS EEE E OLED Test method Min roughness Max roughness Average roughness Min grit size class ISO depth R depth R LDO NG an Z8 HM 100 pinch 0 4 um 16 pinch P180 Portable Rockwell i yO 10 um 400 pinch 2 um 80 pinch A Leeb D DL DC E S N7 nan 10 um 400 pinch 2 pm 80 pinch P120 Leeb G N9 30 um 1200 uinch 7 um 275 uinch P80 Table 2 Roughness requirements Average roughness v
12. A u 5 4 Heavy Use Instructions Equotip Leeb hardness testers are designed for portable applications in industrial environments A few simple precautionary steps can improve the performance as well as prolonging the service life of your device Preparing the Tester e Only use the Proceg supplied or specified mains adapters for charging the instruments battery The device can also be operated directly from the mains adapter without batteries e Equotip cables are optimized to have additional flexibility However it is highly recommended to avoid sharp bends in the cables and sudden loads on connectors these can occur for example if the cables get caught or coiled e Using the test block supplied check your Hardness Tester on a regular basis to make sure it is oper ating properly For more details see chapter 2 4 Checking Test Equipment Instrument Verification Preparing the Probe Minimize dirt build up on the impact device and ensure accuracy by e Removing dirt oil grease and other contaminants from the measuring point e Machining the surface as per chapter Surface Roughness Requirements for Accurate Hardness Measurements See chapter 2 2 Surface Preparation eecececec eee eee eee eee eee eee eee eee eee eee eee seer ese eee eee eee eee eee reser eee eee eee e eee eee ese eres ee eeeeeeeeee reese reese eee eee e eee e eer ere ooo oloo ool o eee eer eeeee ere ee eee eee eeesee eee e ee seee Note Use the
13. Leeb hardness test Part 2 Verification and calibration of the testing devices DIN 50156 3 Metallic materials Leeb hardness test Part 3 Calibration of reference blocks ISO 16859 to be published in 2015 This standard covers the determination of the Leeb hardness of metallic materials using seven different Leeb scales HLD HLS HLE HLDL HLD 15 HLC HLG 4 4 2 Portable Rockwell Method DIN 50157 These standards not only cover the determination of the hardness value of metallic ma terials but also provide useful information regarding the requirements of the test piece surface preparation as well as the test procedure instrument verification check and the documentation of the results including calculation of the uncertainty of the measure ment This standard consists of two parts these are DIN 50157 1 Metallic materials Hardness testing with portable measuring instru ments operating with electrical penetration depth Part 1 Test method DIN 50157 2 Metallic materials Hardness testing with portable measuring instru ments operating with electrical penetration depth Part 2 Verification and calibration of the testing devices Equotip Application Booklet 15 2015 Proceq SA 5 Practical Application 5 1 Conversion of Hardness Measurements Working with different hardness test methods often requires that the hardness measured by one method be converted to that for a different method or strength tensile streng
14. M E140 also contains portable Leeb scales The requirements and limitations in accordance with these standards shall in all cases be followed for any further conversion from one hardness scale to another or into strength values tensile strength in N mm as occasionally required The Equotip 550 offers different options with fast and easy possibilities for the user to create an own conversion curve which perfectly fits onto the material under test An example can be seen in chapter 5 7 Combined Equotip Leeb and Portable Rockwell Measuring Methods 5 2 Influence of Temperature Temperature has some influence on hardness measurements There are different cases which have to be treated differently These are mainly the temperature of the instrument itself and the temperature of the probe The temperature range in which the instrument can be used without any negative influence on the hard ness readings is specified with 10 C 50 C If this range is exceeded correct values can no longer be guaranteed The influence of elevated temperatures of the object under test was researched in a study done by Pro ceq During this study different test blocks were heated up While the temperature dropped several mea surement series were taken Summarized it could be proven that the hardness readings are lower if the temperature of the test block is higher This behavior is dependent on the material under test therefore no correction value can
15. Yes NA o No No No No Yes Yes Yes Yes Yes No D O D Equotip Application Booklet 30 2015 Proceq SA 7 Authors Dr Stefan Frank s educational background is in physics with a doctoral degree in material science from the University of M nster Germany After finishing university he worked for more than ten years as a product manager for non destructive testing equipment including portable hardness testing at Krautkramer and GE Inspection Technologies In 2010 he joined the Siemens NDT Field Service Department with responsibility for training qualification and authorization of NDT personnel His experience in NDT and portable hardness testing has enabled him to achieve several level 3 certifications such as UT VT ET PT and MT Christoph Frehner began as an electrical engineer in Proceq s research and development department For seven years he was involved in the development of a new portable hardness tester in addition to several other technology related projects During the following two years he worked in the European sales office where he built up application experience through customer consultations and technical seminars After completing his MBA he switched to product management with responsibility for metal testing instruments His new function requires active involvement in standardization committees and driving the further development of these products Alireza Akhlaghi is a mechanical engineer sp
16. alues according to DIN 50157 and ASTM A956 To find out more about the influence of the roughness on hardness readings the following experiment was conducted Sample Preparation The surface of a Mn Cr V tool steel was prepared using grinding paper of grit sizes P40 P80 P120 P150 P180 and P240 After each grinding step the surface roughness R was measured using a commercially available surface roughness tester The hardness measurements were taken with Proceq s Equotip Leeb impact device types G D and C as well as with Proceq s Portable Rockwell Probe Equotip Application Booklet 5 2015 Proceq SA Results e Amongst the Leeb hardness testers measurements done with impact device G are least affected by rougher surfaces This is due to the higher impact energy and larger ball indenter radius of impact device G 90 Nmm 5 mm compared to the D device 11 Nmm 3 mm and C device 8 Nmm 3 mm respectively On rough surfaces the indenter of the C device in particular only impinges on surface irregularities giving a low hardness measurement which is not representative of the material Also for the Portable Rockwell Probe the susceptibility to erroneous hardness readings due to surface rough ness is less significant than for Leeb D and C devices The Portable Rockwell device determines the hardness according to the Rockwell principle while using a lower load of 50 N e The scatter of hardness readings taken with impact devices D an
17. be provided The full report on this study can be found in the download section at www proceq com 5 3 Measurement Uncertainty In several cases the hardness testing accuracy is correlated with factors like number of digits shown on the display the price of the instrument or the correlation of the given reading with the expected hardness value Generally these properties have nothing to do with the accuracy of a hardness tester The question How accurate is this instrument then put in this form is actually too inaccurate It could mean that one wants to know how well the instrument measures e g when compared to other stationary hardness testers Equotip Application Booklet 16 2015 Proceq SA However the actual question is whether or not the measured value is correct To answer this question it is necessary to define the term accuracy The factors to be taken into consideration are the systematic and random errors as well as the possible subjective influences of the user The following factors have to be considered when the measurement accuracy has to be evaluated a Absolute Accuracy Systematic Errors or Comparability Absolute accuracy is the instrument s capability to display the correct reading Correct in this con nection means true with reference to an absolute scale This requirement is based on calibration by means of certified reference standards i e such that are traceable to a universal
18. ckwell conversion curve shows the penetration depth of the Rockwell diamond depending on the hardness of the material Test objects should have at least 10 times the thickness of the penetration depth to avoid influences on the measurement value Penetration Depth um S 10 15 20 23 30 43 40 45 si 39 BO 6S r 3 g0 H 50 450 400 450 300 250 40 Wickers Hardness HV JHH saupi Jian 20 i H 100 150 21 i 400 ao ALKI 50 H an n i GO BSO FU Pa BAK Minimum Sample Thickness um Figure 5 Portable Rockwell conversion curve Equotip Application Booklet 13 2015 Proceq SA 4 3 The Equotip 550 The new Equotip 550 is an all in one solution combining the Leeb and Portable Rockwell methods and is compatible with upcoming develop ments such as other measuring principles and new types of probes The new generation display unit with touchscreen leverages the high measur ing accuracy with an unmatched user experience leading to increased measurement efficiency It also comes loaded with interactive wizards handpicked for specific in dustry applications in order to increase reliability and to assure precise measurements including oil amp gas automotive aerospace and steel working applications Leeb rebound hardness testing is mainly used for on site testing of heavy large or already installed metal parts but is also applied for testing composites rubber and rock The Portable Rockwell test method is
19. curacy first in the case of thin Bambino and Pic areas of larger work pieces Tube and pipe colo ref datasheet may be tested with wall as thin as 0 375 for devices C amp G 10 mm so long as the ratio of outside diameter to thickness is less than 5 and the test is performed at least 2 5 50 100 mm away from the tube end 1 25 mm Excellent choice for fast reliable results Yes ref datasheet for devices C amp G Possible but use with coupling method Same as Bambino extremely light parts might require Equotip and Piccolo No G Portable Rockwell or other methods C device possible device might be required Question 2 lt 0 25 Ibs 0 1 kg Sample mass lt 4 5 Ibs 2 kg Possible but the test must be done ona Same as Yes solid support i e granite surface table Bambino and Pic solid concrete floor thick metal plate colo No G device possible gt 11 Ibs 5 kg Excellent choice for fast reliable results Yes G device requires 33 Ibs 15 a Is the surface layer Yes rule of 10x i e case hardening penetration depth lt 0 008 0 2 mm applies refer to manual Is the surface layer Yes with impact Yes i e case hardening device C 0 008 0 032 0 2 0 8 mm Is the surface layer Excellent choice for fast reliable results G device should not Yes i e case harden be used in testing surface layers ing 0 032 0 8 mm Question 3 Surface treatments
20. d Inspection e Clean the guide tube at the end of each working day by inserting the Proceq brush with a rotating and rubbing motion e Clean the support ring and the impact body especially indenter ball and catch pin with acetone e Yearly inspection of the instrument by a Proceq certified Service amp Repair Centre is recommended eeceeee eee eee eee eee eee ee ee eee eee eee eee eee eee see ee eee e eee eee eee eee eeee eee ee ee eee eee eeeeeee eee eee eeeeeeeee eee eee eee ee Note Every week clean the impact device from the inside using an acetone soaked cotton swab and outside using an acetone soaked cloth Cr Proper Storage e Never leave the impact device out on the workbench e Do not coil the cable tightly e Clean the test surfaces of the hardness test block with acetone and cover with Proceg protective sticker e Store in an Equotip case in a dry location at room temperature Figure 8 Maintenance and cleaning procedures Equotip Application Booklet 20 2015 Proceq SA 5 5 Durability Study for Equotip Leeb Impact Devices Objective Proceq Equotip Leeb Impact Devices are Swiss Made and manufactured so as to ensure best in class quality Equotip users value the long term stability of the Leeb hardness scales that Proceq has been providing for over 40 years To highlight this and as part of Proceq s production inspection Proceg con ducted a series of tests to quantify the durability o
21. d and published in 1996 and the next to last edition was published in 2012 This is the only ASTM standard that currently addresses testing with the Leeb method The Leeb method measures the ratio of rebound velocity of a defined impact body launched against a surface at a defined velocity Therefore the Leeb method measures the loss of kinetic energy during impact and this is considered a dynamic technique The accuracy of a Leeb test is dependent on proper test conditions surface roughness test piece thickness and mass which are defined in the A956 standard The A956 standard is not Known to be specifically referenced by any current API standard However the Equotip conveniently converts hardness measurement values and displays the results in other hardness scales such as Brinell Rockwell and Vickers The ASTM standards governing these test methods are generally mentioned in API standards DIN 50156 This German standard is a national standard that includes traceable calibrations of test blocks and instruments to a national Leeb etalon These calibrations are done by ISO 17025 accredited organizations in Germany whose Leeb calibration instruments are traceable to the German national laboratory named PTB Also UKAS calibration of Leeb reference test blocks is now available This standard consists of three parts these are DIN 50156 1 Metallic materials Leeb hardness test Part 1 Test method DIN 50156 2 Metallic materials
22. d especially C increases quickly with rougher surfaces It can be seen that this effect is much less in the data recorded for the G and the Portable Rockwell devices e For the given steel surface impact device G yields reasonably reliable hardness values after surface preparation with P80 grit grinding paper In the case of Portable Rockwell and Leeb impact device type D it is recommended to at least obtain a P120 grit surface finish With impact device C it is pos sible to achieve higher precision results on smaller and thinner samples than with devices D and G however the greater demands on the surface finish are greater P180 grit 450 z i Pa 3 ef n E E m tt 2 C v a oo EE a Oa S J i 350 m m f om g 5 2 i a 300 E Ea co So Oo E S 290 Steel o 12842 O 200 1 0 0 0 6 1 0 1 5 2 0 2 5 3 0 3 5 4 0 45 5 0 Surface Roughness R um Figure 2 Brinell hardness vs surface roughness obtained using an Equotip Leeb Impact Device D Further Provisions e In order to overcome the increased uncertainties of the results due to scatter on rough surfaces the number of readings should be increased and the most suitable impact device should be selected e In case the readings deviate systematically from the actual sample hardness the bias may be ac counted for through a user specific conversion e g an offset This is possible in most Equotip instru ments The individual bias correc
23. d should be prevented The test load should be applied with a steady increase and smoothly following the instructions on the Equotip 550 instrument s display especially when using the Portable Rockwell method The arithmetic mean of at least three measurements per measuring point should be established to deter mine hardness The distance of the centre of each test indentation from the edge of the specimen should be at least 5 mm The distance between the centres of two adjacent test indentations shall be at least 3 times the indentation diameter Care should be taken during the test to ensure that the measuring instrument is operated in accordance with the user manual The determined hardness values should be clearly documented If incorrect function is sus pected a comparison measurement should be performed on hardness standards If the suspicion of incor rect function of the device is confirmed the measurement should be interrupted and repeated with a different device 2 6 Documentation of Hardness Values A record hardness testing report should be prepared on the examinations performed in which all test parameters are to be documented All of the following details should be documented e A reference to the according standard e Details to clearly indentify the test object e Name of tester e Date and time of test e Test instrument with type and serial number of display unit and probe if available e Inspection data e Each sin
24. e relative hardness tests are limited in practical use and do not provide accurate numeric data or scales particularly for modern day metals and materials Equotip Application Booklet 9 2015 Proceq SA In material science and here specifically for metals hardness tests and measurement methods are used which are based on measuring the penetration hardness In this case a standardized indenter is penetrated into the material under defined conditions like test load penetration time or even inspection speed After releasing the load in most cases the geometry surface or depth of the remaining penetration is evaluated This quite general definition allows for different testing methods and principles for measuring the hard ness As a result of this the hardness with respect to metallic materials is measured in many different scales including hardness according to Vickers Brinell Knoop and Rockwell However the numerical hardness values received by the different hardness test methods are not or only conditionally comparable Even worse there is no mathematically universal relation between the differ ent hardness scales If it is required to compare hardness testing results this is only correct if both val ues have been determined with same test method under similar conditions including test load indenter and indentation evaluation In other cases the relation between different scales has to be confirmed by comparative measurements using t
25. e surface of the test piece Today several portable hardness testing instruments based on different physical methods are already particularly recognized in the practical field and solve plenty of mobile hardness testing tasks However each method is limited more or less to a specific application area and therefore the decision which method and instrument to use strongly depends on the testing application With the Equotip 550 Proceg is now offering a solution for a wide range of portable hardness testing ap plications The instrument now combines two well established and widely spread test methods and thus solves the vast majority of conventional hardness testing problems and tasks A detailed description of these two methods is given in the next subchapters Equotip Application Booklet 11 2015 Proceq SA 4 1 Leeb Method Developed in the mid 1970s the Leeb or Equotip method became the first widely accepted portable instrument for measuring the hardness of large components located in the field in a matter of seconds The rebound name comes from the basic nature of the test The rebound method is based on measuring voltages to E 7 indicate the loss of energy of a so called impact body HL 7 1000 7 1000 after it strikes the test piece In an instrument using the rebound principle a spring propels an impact body through a guide tube toward the test piece As the impact body travels unimpeded toward the
26. ecialized in fluid mechanics As a product manager for materials testing he is involved in various standardization committees and the further product development of Proceq s metal testing portfolio Alireza has conducted technical seminars on Proceq s range of hardness testers across the globe Also see book Hartepriifung an Metallen und Kunststoffen Grundlagen und berblick zu modernen Verfahren Konrad Herrmann ISBN 978 3 8169 3181 2 Expert Verlag for further reference to hardness testing on metals Subject to change without notice All information contained in this documentation is presented in good faith and believed to be correct Proceq SA makes no warranties and excludes all liability as to the com pleteness and or accuracy of the information For the use and application of any product manufactured and or sold by Proceq SA explicit reference is made to the particular applicable operating instructions 82035605E ver 04 2015 Proceg SA Switzerland All rights reserved Equotip Application Booklet 31 2015 Proceq SA
27. eeceeceeceeceeeeceecaeseeseeeeeeetauseeeeeseeees 16 5 3 Measurement Uncertainty ccccccccceccecceceeceeceeceecesesenseeceesesons 16 5 4 Heavy Use Instructions ccccceccececceccecceeceseeseeseecescesceseecescesens 19 5 5 Durability Study for Equotip Leeb Impact DeVICES ccceeeeee ee 21 5 6 Using Equotip Leeb Support RINGS cccecseeseeeeeeeeseeteeeeeseeseeees 22 5 7 Combined Equotip Leeb and Portable Rockwell Measuring Methods 24 6 Application Questionnaire cccccsseesscneeeneensseneeenseseeneueneeenseneeenesensenens 27 PUN ONS srir arae REE ses eaueseaesueecueceneveceesssensseee 31 Equotip Application Booklet 2 2015 Proceq SA 1 Introduction The requirements on metallic materials and their practical application in different constructions compo nents installations and machines are increasing continuously Especially aspects like safety and eco nomic efficiency are the main focus as well as potential liability issues which are also to be considered Because of this a reliable characterization of the materials used including a quantitative assessment of the corresponding parameters and material properties play a predominant role In the end materials test ing and characterization mean safety and reliability The selection of a material for a specific application is mainly based on the physical chemical and primar ily mechanical properties The main purpose and
28. ertain position in the guiding tube at the moment of its impact onto the test surface When testing flat samples with standard support rings the spherical test tip is located precisely at the end of the guiding tube However when testing curved samples with the standard support rings this may not always be the case To ensure ac Curate measurements in all cases Proceg offers a range of special support rings designed for measure ments on curved sample surfaces gf A i H 3 Figure 11 Overview of Equotip 550 Leeb Impact Devices and usage of support rings Most Common Test Situations Equotip Leeb Impact Devices D DC C E S and G with Standard Support Rings With each Leeb impact device D DC C E S or G respectively Proceg deliv ers two support rings The 13 5 mm outer diameter OD support ring named D6a provides accurate results if the test surface curvature is larger than R 30 mm The 19 5mm OD support ring D6 can be used down to a minimum test surface curvature of R 60 mm Equotip Leeb G impact devices come with two support rings with 19 5 mm G6a and 29 5 mm OD G6 respectively These provide accurate measurements as long as the surface curvature of the sample _ l has a radius above 50 mm for G6 and 100 mm for G6a rigare Eoo Sei For test surfaces that do not comply with these stan dard situations Proceq s special support rings offer apt solutions for impact devices of types D DC C E and S
29. f its impact devices Procedure The durability tests were performed in an automated way on a customized CNC machine under well de fined and controlled conditions Each impact device was initially calibrated to the Proceg traceable reference A reference test block was then measured according to DIN 50156 2 using 10 impacts spread across the surface of the test block The average hardness value was calculated and checked against the given tolerance The complete pro cedure was repeated with test blocks of different hardness levels for various types of impact devices Results The results are shown in the table and graphs below For each test the out of tolerance point was reached due to wear of the impact body whereas the impact device itself still was in good condition An Equotip Leeb G impact device is typically used on heavy duty castings and forged parts and aver ages a hardness often around 35 HRC or 325 HB Thus the impact body is expected to reach a lifetime of 100 000 impacts based upon a hardness of 35 HRC The very versatile Equotip D Leeb impact device is found to last longer than device G which is mainly due to the smaller indenter sphere as well as the lower impact energy To many users such a lifetime es sentially means that the impact body never has to be replaced Once the hardness of the test piece ap proaches 60 HRC the impact body D device out on hardness level before drift 4 HL wears out faster This i
30. gle measurement reading in the native unit and if available in the converted unit e Statistical values such as mean value standard deviation span etc e Any significant detail such as sample preparation coupling impact direction test location tempera ture etc e Any notes and photos Equotip Application Booklet 8 2015 Proceq SA 3 The Definition of Hardness From a technical point of view the hardness is considered as the resistance of the material against the penetration of a specific and typically harder indenter Depending on the indentation system which in cludes the indenter itself as well as the test load applied different hardness values or scales are used in the practical field Therefore hardness is not a fundamental property of a material but a response to a particular test method Basically hardness values are arbitrary and no absolute standards for hardness exist Hardness has no quantitative value except in terms of a given load applied in a specific repro ducible manner and with a specified indenter shape Considering this the definition of hardness clearly differs from that of strength which describes the resistivity of a specific material against deformation and separation But hardness is also used in order to describe the wear resistance of materials E g hard eyeglass lens es are more resistant against potential scratches heat treated gear teeth wear down slower hardened blades or knives stay s
31. harp longer Nevertheless in some cases a higher hardness is correlated with an increased brittleness which unfortunately is the other side of the coin In a word hardness testing is considered to be a quick relatively inexpensive nondestructive test which is used to characterize materials and determine if they are suitable for their intended use Determination of Hardness Values Hardness of materials has probably long been assessed by resistance to scratching or cutting An ex ample would be material B scratches material C but not material A Alternatively material A scratches material B slightly and scratches material C heavily Relative hardness of minerals can be assessed by reference to the Mohs Scale that ranks the ae of MAEA to resist scratching by another material Mineral Chemical formula Mohs nnn hardness _ Taic MgSO OH 1 Ge coco o ee cco o o Fuorte CaF O 4 Apatite Ca PO FCIOH 5 az Feldspar KASO 6 oa DOM o e ee on ane 7 Ao o i eee Figure 3 Mohs scratch tool Similar methods of relative hardness assessment are still commonly used today even for metallic materials An example is the file test where a file tempered to a desired hardness is rubbed on the test material surface If the file slides without biting or marking the surface the test material is considered to be harder than the file If the file bites or marks the surface the test material is considered to be softer than the file The abov
32. hat must be considered Generally because of the relatively small indentation created by the Portable Rockwell it is best suited for testing fine grained materials with a variety of shapes and sizes Rebound testers produce larger in dentations for more consistent results when testing large coarse grained materials typical of forged and cast components Consistency of test results requires the indentation size to be large in comparison to the material s mi crostructure Therefore rebound instruments with their larger indentation should be given first consider ation over Portable Rockwell instruments when testing coarse grained materials It should be evident from the above discussion that there is not one general purpose portable hardness tester capable of handling every test Each of these methods is utilized for its specific application range A general overview is illustrated in Table 1 Application overview 1l Leeb Probes in combination with correct support rings Table 1 Application overview Using equipment that fully matches the respective application is a very important factor in portable hard ness testing as it will ensure the best results and minimize false readings A comprehensive guide for selecting the best suited test equipment can be found in chapter 6 Application Questionnaire Equotip Application Booklet 4 2015 Proceq SA 2 2 Surface Preparation One of the biggest mistakes is trying to test a s
33. he different scales involved The topic see chapter 5 1 Conversion of Hardness Measurements is quite important and thus will be discussed in a separate section of this paper Equotip Application Booklet 10 2015 Proceq SA 4 Portable Hardness Testing The development and application of hardness testing instruments is characterized by the shifting of the testing tasks from using stationary machines in the laboratory to mobile on site measurements during the production process Large parts or those with surfaces that are difficult to access are the prime reasons to consider or for considering portable hardness testing In response to the need to test products that are too large for con ventional Rockwell Brinell or Vickers hardness testing methods quality and manufacturing profession als are making more use of portable hardness testers For production testing the ability to test complex shapes and access difficult test areas allows portable testers to complement stationary testers Portable Hardness Testing Methods Two of the methods most commonly used by portable hardness testing instruments are the Leeb or re bound method and the Portable Rockwell principle Mobile hardness testing instruments will not replace the conventional bench top machines but neverthe less they have become an indispensable addition for hardness testing units During the last decades several portable instruments based on different physical meth
34. m 2 73 inch while for Leeb C a mass of 1 5 kg 3 3 Ibs and a thickness of 15 mm 0 59 inch are already enough Specimens with masses less than the minimum mass specified in DIN 50156 1 and ASTM A956 Leeb or specimens with sufficient mass but with areas thinner than the indicated minimum thickness require a heavy support and or coupling to a solid object The requirements for coupled objects can be taken from Table 3 Minimum requirements on mass and thickness of samples according to DIN 50156 1 and ASTM A956 ee enna nny D DC DL ES food A Min weight of samples of compact shape 5kg 11 Ibs 1 5 kg 3 3 Ibs 15 kg 33 Ibs _on solid support 2 kg 4 5 Ibs 0 5 kg 1 1 Ibs 5 kg 11 Ibs coupled on plate 0 05 kg 0 2 Ibs 0 02 kg 0 045 Ibs 0 5 kg 1 1 Ibs Min thickness of samples __ uncoupled 25mm 0 98 inch 15mm 0 59inch 70 mm 2 73 inch coupled 3 mm 0 12 inch 1 mm7 0 04 inch 10 mm 0 4 inch surface layer thickness 0 8 mm 0 03 inch 0 2 mm 0 008 inch Table 3 Minimum requirements on mass and thickness of samples according to DIN 50156 1 and ASTM A956 If a sample has to be coupled to a larger mass the following steps have to be followed e The contact surface of the sample and the surface of the solid support must be level flat and ground smooth e The sample must exceed the minimum sample thickness for coupling Follow the coupling procedure e Apply a thin layer of coupling paste to the contact surface of the sample e Press the sam
35. o deviating results The less an instrument depends on the way it s operated by differ ent persons the better its reproducibility d Errors caused by the Test Object There s naturally no such thing as the ideal test object especially not in hardness testing Sur face roughness crystalline structure and hardness homogeneity on the test surface remarkably af fect the hardness measurement irrespective of the test method Errors caused by the test object are often or even in most cases the very fact that puts inspectors and operators into a state of uncertainty as any possible variation of measured values caused by the test object s properties are wrongly mistaken for instrument characteristics such as comparability and repeat ability But what can be done in order to receive reliable hardness values Statistics will help here eeccececer ecco eee eee eee eee eee eee eee ese eee eee eee ese eee eee eee ese eee eee ee eee eee eee eee eee ees e ree e ees eee ee eee eee eee ee eee eee eee eee eee eee eeeeseeeeee ese eZee eeeeeeeee eee eeeeeeee reese ee eeee Note A single reading is no reliable criterion with regard to the hardness of the test object The aver age hardness can only be determined after a corresponding a number of measurements has been made The larger the number of measurements the more reliable the determined hardness value Another positive side effect of this statistical contemplation of hardness testing i
36. ods were developed Today mobile units are widespread and accepted tools for portable on site hardness testing applications Hardness testing can be considered as portable if the test equipment can be transported by one person without any additional support or utilities In addition to this the determination of the hardness value has to take place directly on site after the actual measurement on the component Applications for Portable Hardness Testers The main advantage of portable hardness testing equipment is as the name suggests the portability of the test equipment The test piece no longer needs to be cut and to be brought to the hardness tester today mobile handheld instruments allow measurements to be made on the spot Even big or heavy components can be tested without having to be moved In addition to this portable hardness testing equipment allows measurements on difficult to access positions or during the production manufacturing or assembly process Furthermore in contrast to typical stationary hardness testing machines using the Vickers Brinell or Rockwell principle the use of portable equipment is not limited to the perpendicular position With Proceq Equotip 550 equipment measurements in different positions and directions are possible without having to think about any corrections or adjustments The only limitation to be consid ered here is that the hardness probe has to be positioned perpendicular with respect to th
37. ple firmly against the support e Push the sample in a circular motion and carry out the impact as usual perpendicular to the coupled surface 2 4 Checking Test Equipment Instrument Verification All applicable standards recommend performing a simple equipment test before and after material testing In this indirect check measurements are performed on certified hardness reference blocks in the correspond ing hardness range to verify the sound operation of the test equipment Leeb Method The DIN 50156 1 Annex A requires a test consisting of at least three indentations on a hardness refer ence block calibrated in line with DIN 50156 3 and or ISO 16859 3 If the difference between the mean value for the read hardness and the hardness of the reference block is lt 15 HL and the maximum range is lt 15 HL then the instrument can be considered satisfactory If not indirect verification should be performed According to the ASTM A956 the test instrument should be tested with two indentations on a standard ized test block These two readings must fall within 6 HL of the reference value to verify that the instru ment is working properly Equotip Application Booklet 7 2015 Proceq SA ISO 16859 1 Annex B is based on the DIN standard and therefore the procedure is similar Only the acceptable levels are defined differently with a maximum deviation of lt 5 of the mean value from the reference value and a maximum span of lt 5
38. proce Equotip Application Booklet Portable Hardness Testing Using Leeb and Portable Rockwell Table of Contents 1 WEE CC HON acerca scat ec eee eee re mse eee ccc es eee eect seo bees a seceneecdoncencuees 3 2 From Specific Application to Reliable Hardness Values 0000 4 21 Method Solc ON eee eE EEEE ESS 4 Zee SUNCE PED O e E AEE E ER E EES 5 2 3 Mass and Wall Thickness LIMItations cc eccceeeeeeeeeeeeeeeeeeeeeeeenees 1 2 4 Checking Test Equipment Instrument Verification c ccceeceeees A 2 5 Execution Of MEASUPEMEeNMS cccecceeeseceseceeeeeesseeeeteoeeseeeeeeseeees 8 2 6 Documentation of Hardness Values ccccccseeceeeneeeeeeeeeeseeeseeeeeens 8 The Definition of Hardness cssccsscsssssssnscnsenssnsenssnssensenssssensensesess 9 Portable Hardness Testing waveseuncsinsccewseuntecvecteceuseaansceweceeseencansaecausveuseans 11 d WCCO MEONOO sesira e e EEEE 12 4 2 Portable Rockwell Method s sssnssnsnssnnnnnnsnnnsnnnnennnnsrrnnnrrnnnrennenrennne 13 AES MINS EGUO DOO sancscancecnasscennaeatseicanaaeuranaanesssicaadecieemmiennsiecoatmmnangeaans 14 4 4 Standardization for Portable Hardness Testing secceeeeeeeeeeee 14 5 Practical Application wescccssceencedsscsaredussuwacdewawawercausessscacsesseeassuatenscstwsvebnesst 16 5 1 Conversion of Hardness Measurements cccseccseceeeeeeeeeseeeseeens 16 5 2 Influence Of emperature cccec
39. quires 1 6 um 63 winch ISO N7 Ra for best results Yes requires 1 6 um 63 inch ISO N7 Ra for best results Yes up to ISO 12 5 um 492 winch ISO N10 Ra or better with impact device G Ra lt 2 um 63 inch to minimize data scatter Possible if test piece is long enough to span clamp reference cap with Z2 support Yes suggest using special support rings for radius between 10 mm and 50 mm Z series Special feet and supports available Yes with DL accessory Kit confirm Yes through empirical data DL Device Yes use of special support rings for radius between 11 mm and 30 mm HZ series Yes with DL accessory Kit confirm through empirical data DL Device Yes suggested use of special support rings for radii between 11 mm and 30 mm HK series Yes suggested use of special support rings for radii between 10 mm and 50 mm K series Equotip Application Booklet 28 2015 Proceq SA Instrument Feature Considerations Display Specification Equotip Bambino 2 Equotip Piccolo 2 Equotip 550 Leeb Equotip 550 Portable Rockwell Hardness HRA HRB HRC Yes refer to data sheet for impact Yes refer to Yes also 15N 15T Scale HV HB HS tensile devices impact device D amp DL only data sheet for im MMRC HRE HRH strength pact devices reference data sheet all possible for ranges Impact Other than down Yes all impact directions Yes all impact direc Di
40. rection automatically possible tions possible with automatic detection of direction Other than ferrous Yes refer to datasheet impact devices Yes refer to data Yes metals impact device D amp DL only conversion to sheet impact de scales as listed vices all possible Conversion to other scales as listed Hardness reading a Yes Statistics averag Yes a Std Dev Instrument setup e Yes All of the above dis Yes played at same time Backlight Ooo o o o Yes Yes User C E ee ee a ntrerface Interactive guides _ E Ss Automatic verification Combination method for hardness testing Sime menu Yes es ss Selectable display of Yes data hardness his togram stats etc User profiles instru Yes ment setup with password protection Communica tion Type No Slave USB Master USB slave Master USB slave USB Ethernet Pro USB Ethernet Pro ceq serial interface ceq serial interface wes wo o w SN Automation remote No No Yes Yes functionality Equotip Application Booklet 29 2015 Proceq SA Specifications Specification Equotip Bambino 2 Equotip Piccolo 2 Equotip 550 Leeb Equotip 550 Portable Rockwell Test Power supply Battery or AC Battery or AC Lithium polymer Lithium polymer environment 3 6 V 14 0 Ah 3 6 V 14 0 Ah Immersion resistant Limited electronics integrated with im Limited but impact device separate from pact device Immersion or heavy
41. s no mathematical relationship between different test methods it is a common practice to correlate them with one another The existing default hardness conversions in Equotip Leeb devices are based on specific sample geom etries A Portable Rockwell probe has almost no restriction with regard to thickness and mass For sam ples that don t meet the Leeb specification a simple custom correlation based on the Portable Rockwell measurements enables the user to apply a correction factor and create a new hardness conversion This can be achieved following the combined method wizard on the Equotip 550 This wizard guides you in five simple steps through the whole process and finally creates the conversion curve for you Step 1 Choose the Equotip Leeb probe with its corresponding settings Combined method 1 5 Select Equotip Conversion Probe Equotip Leeb Impact Device D gt Material Steel and cast steel gt Conversion standard Default gt HV V Vickers gt Figure 21 Screenshot of settings for the Leeb measurements Step 2 Choose the settings for the Portable Rockwell measurements Combined method 2 5 Select Portable Rockwell Probe Conversion Conversion standard Figure 22 Screenshot of settings for the Portable Rockwell measurements Step 3 Equotip Application Booklet 24 2015 Proceq SA Prepare your sample according the requirements for your selected probes For more details please refer
42. s the fact that the above mentioned errors which may occur both as positive and as negative deviations from the real hardness value are also partly reduced by averaging using many single readings eeeeeeeeec cece eee eee eee eee eee eee eee eee eee eee eee sere ee eee eee eee sere eee ee eee eee eee eee eee eee eee eee eee eee eee eee ee eee eee eee ee eee eee e eee eee ee eee eee eee e eee eee ese eee ee eee eee ee seeeee Equotip Application Booklet 17 2015 Proceq SA How many Readings should I take If more individual readings are used to obtain the final result we can be more certain that the calculated average is closer to the actual hardness of the test piece However performing more measurements re quires extra effort and the overall improvement of the data will be marginal at some point e Asarule of thumb anything between 3 and 10 readings is generally acceptable unless stated otherwise e Taking 10 readings is a common choice as this reduces the statistical uncertainty averages outlays and makes the arithmetic easy In some cases taking 3 readings is sufficient this practice is common where test pieces are comparatively homogeneous in hardness e Using 20 or even 50 only results in a slightly better estimate than 10 Probability of occurrence l Mean or average value l Mean or average value i Value of reading Value of reading l Figure 6 Distribution of readings However a detailed eval
43. s where the impact 550 HLG 35 HRC 400 000 device S iS useful showing exceptional She ee AE salbnspacbsa stead netes cpensawageasaaeassieds A fededed E aaced ET OPE E E EEE EEEE aaussieudendededsicmbaned E ETEA durability even at 61 HRC The Equotip SPOE a a e ee P oe ee Leeb S impact device is only outdone by D 775HLD S6HRC gt 300000 the E impact device results not shown D 820 HLD 61 HRC S000 which uses a diamond indenter sphere and 830 HLS 61 HRC gt 200000 shows no wear after many impacts on very For D device on 600 and 775 HLD impact device and body still worked reliably hard tal even after 300 000 impacts With all the other tests the impact body was the ara metals limiting factor Figure 9 Overview durability test results Selected Wear and Tear Trend Curves Overall the tests re confirm the well recognized high performance standards of Equotip Leeb impact devices Please note that results can vary depending on the surrounding environment e g dirt metal dust handling etc where the testing is taking place A rough environment can have a negative effect on both the impact device and body Drift HL T Number of impacis Figure 10 Drift of measurement values in relation to number of impacts performed Equotip Application Booklet 21 2015 Proceq SA 5 6 Using Equotip Leeb Support Rings Leeb hardness testers provide accurate measurements if the impact body has a c
44. surface roughness comparator plate provided in order to meet the required sur face condition for the test method principle e Removing metal dust and abrasive grit with a cloth e Placing the sample on a solid support base or in a holder fixture depending on its mass thickness For more details see chapter 2 3 Mass and Wall Thickness Limitations Measurement Procedure 1 Hold the black loading tube with your index finger middle finger and ring finger on one side and your thumb on the other side With the other hand hold the coil casing as close as possible to the support ring 2 Load the impact device in the air by slowly and evenly sliding the loading tube as far as it will go in the direction of the coil housing Then slowly draw the loading tube back never allowing it to snap back abruptly eecececeee eee eee eee eee ee see eee eee ee sees seeeeeeeeeeeeeeeeeeeeeeee ese eee eeeeeeeeeeeeeeseeeeeeeoee eee eee oH eH oO HOO HOHE HOH EOE eoceeeeeece eee eee eee eee eee eee eee ee eee eee ee eeeee eee eee eee eeeee eee eee eeeeeeeeeee eee eee eeeee eee eee eee HEHEHE HOHE EOE OOO 3 Slightly depress the release button with your thumb and wait for Figure 7 The Leeb measurement approximately 1 second procedure in three steps Note When performing measurements wear clean gloves and take extra care not to touch the guide tube with dirty hands Equotip Application Booklet 19 2015 Proceq SA Routine Maintenance an
45. th in N mm lf a measured hardness value is meant to be converted into another scale i e into the result of a com pletely different hardness testing method there is no mathematical equation for doing this Generally there are no applicable relations for converting hardness values from one to the another So called conversion tables are therefore empirically determined thus involving a certain amount of ex periments To do this the hardness of a certain material is measured using the different test methods and the relation between the individual scales is determined Such conversions can only be carried out if the conversion relation has been statistically safeguarded by a sufficient number of comparison measurements Moreover it should be taken into account that conversion relations taken from national and international standards are restricted to certain material groups Because of the necessary experimental determination of the conversion curves for different materials errors should be taken into account here due to which there will be a corresponding factor of uncertainty when converting into another scale Empirical values have therefore been determined based on a large number of comparison measurements conversion tables prepared and the values standardized in the corresponding ASTM E140 or ISO 18265 standard formerly DIN 50150 While in ISO 18265 conversion tables are available between the different stationary hardness scales AST
46. tial but avoidable inaccuracies or measurement deviations As a result of this portable hardness testing equipment was considered in the past to be inaccurate and not usable as a measuring device but only for a rough estimation of the real hardness value The root cause of this wrongful reputation is not based only on the capability of the portable hardness testing equipment itself but is mainly a result of erroneous utilization of the instruments However the user is not really to blame for that because the necessary documentation standardization as well as training and application support were available at that time Recent activities with respect to training and even more importantly standardization of the different portable hardness testing methods are providing the basis for reliable and repeatable hardness results This remarkably increases the accep tance of hardness test results measured by portable instruments and facilitates the use of those devices Currently there are several national as well as international standards for portable hardness testing available Equotip Application Booklet 14 2015 Proceq SA 4 4 1 Leeb Rebound Test Method ASTM A956 Standard Test Method for Leeb Hardness Testing of Steel Products The Equotip Leeb series of hardness testers are standardized in ASTM according to A956 06 Standard Test Method for Leeb Hardness Testing of Steel Products This standard was originally approve
47. tion needs to be worked out through measurements on two samples one rough one smooth that have the same hardness Summary Depending on the test application different hardness tests and probes can be used The selection of the right instrument should be based amongst other things on the surface preparation As a general rule for hardness tests the better the surface condition the more accurate and reproducible the measure ment results During surface preparation however it is critical not to alter the hardness through hot or cold working In case surface conditioning has to be limited for economic reasons utilities such as user specific conversions or adaptations of the testing procedure should be considered Equotip Application Booklet 6 2015 Proceq SA 2 0 Mass and Wall Thickness Limitations The wall thickness and mass of the test object can influence hardness testing according to Leeb Appli cable standards require a minimum wall thickness and minimum mass If these requirements cannot be fulfilled additional measures such as coupling or supporting the specimen are necessary Requirements for the Leeb method impact device D DL DC E and S are that parts must weigh at least 5 kg 11 Ibs and have a minimum thickness of 25 mm 0 98 inch to prevent them from yielding or flexing under the large force created during the time of impact For the Leeb G this is accordingly higher with a mass of 15 kg 33 Ibs and a thickness of 70 m
48. to chapter 2 2 Surface Preparation eeeereee cece eee eee eee eee eee eee eee eee eee eee ee eee eee eee eee ee ee eee eee eee eee eee eee eee eee eee eee eeeeee eee eer eee ee eseeee eee ee ee ee eee eee eee eee eee eeee eee eee ee ee eee eeeeeeeee reese eeeee Note Sample preparation is a critical factor and should be done prior to testing in order to avoid any undesirable discrepancies Figure 23 Preparation of test sample and marking of the test area Mark an area for testing on your sample and perform the test with your Equotip Leeb probe A rF i PK T ie m Figure 24 Performing Leeb measurements on test sample JE Combined 772 HLD 5 4 6 HLD 768 781 HLD Equotip Application Booklet 25 2015 Procegq SA Step 4 Perform the testing with your Equotip Portable Rockwell probe on the same area Mt Damore 729 3 HV L640 HY TIZA 761 7 HW Step 5 Before creating the curve a summary is shown with the results obtained Note There is a significant difference between the Portable Rockwell and the Leeb default con version values eecececee reece eee eee eee eee eee eee see eee eee eee eee ese eee eee eee eee eee eee eee eee reece reece eee ees e reser ese eee eee eres eee soe eee eeer eee e eee eee eee eeresreeee eee ee ree eeee reese eee eeeeeee eee eee essere Combined method 5 5 ani at Tt uy in a summary Leth Impact Device mean walte Ti Led ALD Portable Rock
49. uation of the measurement uncertainty considering all the influencing factors mentioned above e g according to DIN 50156 or DIN 50157 is quite extensive Therefore a simplified evaluation method can be used here in order to analyze the effect of measurement uncertainty It must be accounted for here that the standard deviation for a small number of measurements can only be estimated A correction can be made for small measurement series using the so called Student s f dis tribution or simply f distribution The standard measurement uncertainty u is thus calculated as follows f s vn u standard measurement uncertainty u s standard deviation n number of measured values f t factor If e g 5 measurements are made for each hardness testing measuring point the corresponding t factor of 1 14 will be accounted for while in case of 3 readings the t factor is 1 32 Practical Example On a test block with a given hardness value of 630 HLD the following five values were measured 628 631 636 624 633 The arithmetic mean H is 630 4 HLD The standard deviation s is 4 62 HLD n is obviously 5 and f is 1 14 With these parameters the standard measurement uncertainty can be calculated using the formula given above The value is thus f s_ 1 14 4 62 HLD eo ae 2 36 HLD This means now that the real hardness value lies within the range of H u resp 628 04 632 76 HLD Equotip Application Booklet 18 2015 Proceq S
50. urface without smoothing it out to clean grease or remove paint Because hardness testing is a surface related test anything that gets between the metal and the hardness test indenter is going to influence the hardness measurement and will thus lead to remarkable measurement deviations in the worst case The following points regarding the test object surface preparation and performance of the measurement should be observed in order to obtain reliable measurement results e Hardness testing using portable equipment can be performed on objects with differing shapes pro vided that the hardness tester can be positioned vertical to the test surface and the area for testing is flat and smooth For non flat surfaces please see chapter 5 6 Using Equotip Leeb Support Rings e The test area must be prepared such that changes to the surface due to heating or cold deformation remain restricted to a minimum Scale foreign objects or other surface imperfections must be com pletely removed In particular the surface should be free from lubricants Surface roughness has a significant effect on the repeatability of the measurement with the result that rough surfaces must be prepared accordingly In an initial step all foreign material such as rust and scale is removed from the surface which is then ground and polished Tools such as flap wheel grinders with P120 P240 and P320 or finer grits are used Work is started with P120 grit and is completed
51. well Probe mean value TARS HV Offset 106 HV Ea i i Figure 27 Summary screen and new created conversion curve eeeereeeec eee ec eee ee eee eee eee ee eee eee eee eee eee ee eee eee eee ee eee ese eee ee see eee eee eee eee eee eee ee see eee eee eee eee eee ese eee ese ee eee eee eee eee eee eee eee eee eee eee eee e eee eee eee eee ese ee ee Note There is a significant difference between the Portable Rockwell and the Leeb default con version values The curve has now successfully been created and is stored on the instrument Choose the new material curve you ve just created from the main measuring screen Now the hardness test results from Equotip HLD should match the measurements in the desirable scale obtained by the Portable Rockwell probe and testing can be extended to the heat affected zone and the weld with the Equotip HLD probe Equotip Application Booklet 26 2015 Proceq SA 6 Application Questionnaire Date Proceq contact Ce ooo o ooo o ooo o coocoo oo olll bllblllsblsablsMltMb ltl ltaMlstIltM ltsMltM ltsMltM ltIMl snMl sM sIo sML sM solsolsnolsIoso sIolsoLlsoGso sosnLlsnoGsnososnososososoososooso soso T Prime contact End user E mail Address Question Specification i i ip Pi Equotip 550 Equotip 550 Portable Rockwell Question 1 lt 0 125 3 mm Yes 1 mm limit al ae lt 1 25 mm Possible but use with coupling method Same as Equotip or verify ac
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