Lab Data Sheet Lab-04

Engineering 45
Brinell & Rockwell Hardness for Flat Stock
Lab-04 /

Lab Data Sheet – Lab-04

Lab Logistics

Experimenter:
Recorder:
Date:
Equipment Used (maker, model, and serial no. if available)

Directions

1. Instruments & Supplies

· Pittsburg Instrument & Machine Brinell Hardness Tester, s/n 1909

· Buehler “Rockwell Hardness” Tester

· Belt Sander

· Steel Rule

· Diamond Scribe

· Digital or Dial Calipers, 1 mil resolution or better

· One or More Flat Metal Hardness Test Specimens

2. Specimen Preparation – for each Sample

· The Brinell indentation is measured with a Low-Power, Hand-Held microscope.

o To ensure the that there is good contrast between the specimen surface and the specimen dent-edge, LIGHTLY polish the measurement-surface, or test-face, using the belt sander on the bench next to the Tensile Tester

§ PERSONAL PROTECTIVE EQUIPMENT is required for Grinding

· Eye Protection; either your own eyeglasses, or a Face-Shield provided by the instructor

· Leather Gloves

· Brinell Hardness tests use a 10mm ball-indenter; with a maximum expected indentation chordal-diameter of about 6mm.

o The instrument manufacturer specifies the minimum test-to-test center-distance as 2.5 indenter-diameters, or about 15mm (0.6”)

· Each flat specimen will be used for multiple measurement tests. To yield maximum measures per sample, and to maintain the required test-to-test distance each specimen will be Grid-Ruled to delineate valid test locations.

o Use a Steel-Rule and a diamond scribe to mark a 15mm X 15 mm grid on the test-face

§ Place the grid to maximize the number of test-squares; i.e., minimize the edge loss

· At the completion of this step, the test specimen should contain a “shiny” test-face with a 0.6”x0.6” grid

Figure 1 Flat Specimen BHN and Rb Measurement Points within 15mm Grid Field

3. Specimen and Test Protocols:

· Multiple tests of TWO different test-types will be performed on the SAME specimen

o As indicated in Figure 1 each 15mm X 15mm grid field will tested at 5 points in this sequence

§ Four Rockwell Hardness tests in the corners of the grid field as shown in Figure 1.

· Operate the Rockwell tester in accordance with the instructions given in Lab-03.

· Enter the Rockwell hardness values in the appropriate data table.

· Note that most specimens will test on Rockwell “b” scale, but some of the softer materials may use other scales. See the individual data tables.

§ Make One Brinell Hardness measurement in the center of grid field as shown in Figure 1.

· Be sure to apply the proper load for the given material; either 500kg or 3000kg; depending upon the expected hardness. See the individual Data tables.

4. Instrument Preparation

· If needed on the Rockwell tester replace the round-specimen anvil with the flat-specimen anvil

· If needed on the Brinell tester, hang the counter-weights for the automatic 3000kg load application.

5. For Each Specimen, prior to the start of the Hardness Testing, Measure:

· The Specimen thickness with a calipers to a minimum resolution of 0.001” (1 mil)

o Record the Thickness measurements in the appropriate data table

6. Rockwell Hardness Testing

· Operate the Rockwell tester in accordance with the instructions given in Lab-03.

· Perform the four tests, and Record the hardness measurement in the appropriate data table.

7. Brinell Hardness Number (BHN)Testing

· Using the handwheel, lower the anvil to accommodate the sample

· Slow raise the sample until the Ball indenter makes contact in the grid center.

o The initial contact should be slight, but sufficient to hold the sample in place

· On the control section of the instrument, CLOSE the hydraulic-pressure relief valve.

o The instrument is now ready for the application of the major load

§ Two major loads have been defined for BHN testing:

· 500 kgf for softer materials

· 3000 kgf for harder materials

· If using a 3000 kgf load then

o Increase the load as indicated on the gage by pumping the pressurization lever.

§ When the instrument reaches a 3000 kgf load, the counter weights will rise to fix the load force. Discontinue the pumping action.

o Allow the load application to persist for at least 15 seconds.

o Release the specimen by SLOWLY opening the pressure relief valve

o Lower the anvil using the handwheel and remove the specimen

· If using a 500 kgf load then

o Increase the load as indicated on the gage by VERY SLOWING pumping the pressurization lever.

§ When the gage reaches a value of 500 kgf IMMEDIATELY discontinue the pumping action.

· Overloading the specimen will invalidate the test and must then be repeated

o Allow the load application to persist for at least 15 seconds.

o Release the specimen by SLOWLY opening pressure relief valve

o Lower the anvil using the handwheel and remove the specimen

8. Use the 20X “Brinell Microscope” to measure the indentation diameter, Di, in mm

· Measure the indentation TWICE in roughly-orthogonal directions to compensate for any non-circularity associated with any given indentation.

9. Repeat Steps 6-8 until all hardness measurements have been completed for 2 grid-fields on a given sample

10. Repeat Steps 5-9 until all measurements on all bulk samples have been completed

11. Penny Test – Before/After 1982

· Prior to 1982 the USA Mint Struck the penny coin from pure copper. Then, in a cost saving move, the Mint converted to a Zinc-body/Copper-plated coin (http://www.pennies.org/hr_433.html). New pennies consist of about 97.5 wt% Zn and 2.5 wt% Cu.

o Use the Rockwell tester to assess the durability of the new penny compared to its predecessor

· Set the Rockwell Test for the “H” Scale

o 1/8” Ball indenter

o 60 kgf major load

· Locate two pennies; one Pre-1982, and one Post-1982

· On the “heads” side of each coin measure the Rh values at two locations

· Enter the values in the appropriate field in the data table.

12. Return all lab hardware to the “as-found” condition

13. Reduce the Data, and consult the published literature required to complete Table I thru Table VIII

· Calculate the BHN using the Load/Area Formula given in Appendix 2.

Appendix 1- Fundamentals of Brinell Testing

Ref: http://www.hardnesstesters.com/brinell.htm

Widely used on castings and forgings, the Brinell test method applies a predetermined test force to a carbide ball of fixed diameter which is held for a predetermined time and then removed. The diameter of the indentation width is measured twice - usually at right angles to each other and averaged. A formula or chart is then used to convert the averaged diameter measurements to a Brinell hardness number.

Test forces usually range from 500 to 3000 kilograms (occasionally down to 1kg in less frequently used tests). Carbide[1] indenters are 10mm in diameter, although there are less frequently used tests using light loads and smaller diameter indenters (from 5mm to 1mm). Generally, the test load must be held for 10 - 15 seconds although in practice shorter dwell times are often used if it is known not to influence the test result. The Brinell measurement is typically done to the nearest 0.05mm and occasionally 0.01mm although using a standard 20X scope such a measurement is subject to operator influence.

There are limitations and conditions in the use of the Brinell test. The test surface may need to be prepared with a grinder to make the test area brighter so the impression is measurable able using the scope, to remove hardness surface effects from heat treating, or to smooth the surface to produce an even impression. Other conditions limit the use of a Brinell test: on materials that are too thin (less than ten times the depth of indentation); locations too close to the sample edge (less than 2-1/2 impression diameters); or too close to another indentation (less than 2-1/2 impression diameters). Other conditions require the direction of the load to be perpendicular to the test surface within 2 degrees. Curved surfaces should be at least 2-1/2 times the diameter of the ball diameter being used.

Appendix 2- Brinell Test Background Information

http://www.azom.com/details.asp?ArticleID=1406

Background

The hardness of a material is defined as its resistance to another material penetrating its surface and is related to its wear resistance and strength. Higher hardness is related generally related to higher strength, which in turn is related to its structure. It is also a measure of a materials resistance to plastic deformation.

Brinell Hardness

The Brinell hardness test is suitable for a range of materials hardness’. Brinell hardness testing involves forcing a hardened steel ball (or a tungsten carbide ball for extremely hard materials) into the surface of the specimen. The ball usually has a diameter of 10mm and is pressed into the sample using a predetermined load dependent on the relative hardness of the material e.g. 500kg for softer metals and 3000kg for hard metals.

The load is applied for a defined time, usually 10-15 seconds and the impression diameter measured using a low power microscope.

Calculating Brinell Hardness

The hardness is then calculated as a ratio of the load to the curved surface of the impression using the equation:

where:

· HB = Brinell hardness

· F = load in kgf

· D = the diameter of the indenter in mm

o 10 mm for the Chabot College Instrument

· Di = impression diameter in mm

Advantages of Brinell Hardness Measurements

Due to the size of the indenter and the impression, the Brinell system is more indicative of the bulk material hardness compared to other techniques which test over a much smaller area and may in fact be measuring impurities or inclusions.

Brinell Hardness Measurement

Brinell Hardness is a measurement in which a 10 mm diameter steel ball, D, is impressed onto a surface of the sample to be measured. The load commonly used for ferrous metals is 3000kg (For nonferrous metals it is 500 kg). The impression is made for a period of at least 15 seconds, after which the indenter is removed and the diameter of the impression, d, is measured. The Brinell Hardness Number BHN (With units of kg/mm2)is computed by dividing the Load by the Indentation Area. A schematic of this measurement is shown below:

· BHN=[Load/Area-of-Indentation] (kg/mm2)

Table I – OFHC Copper (C10200 Electrical Bus-Bar Material) Test Date

Hardness Scales

§ Rockwell Scale = B (1/16” Ball, 100 kgf load)

§ Brinell Load = 500 kgf

Specimen Thickness Measurement =

Specimen Hardness Measurements

Test No. / Rb / BHN Di1 / BHN Di2 / BHN Diavg / BHN (kgf/mm2)
1
2
3
4
5
6
7
8
Avg

NOTES

1. Microscope measurements for Di1 and Di2 should be done at RIGHT-ANGLES to each other

2. The quantity Diavg = [Di1 + Di2]/2

Table II – A92024-T4 ALUMINUM (4.5Cu, 0.5Mn, 1.5Mg) Test Data

Hardness Scales

§ Rockwell Scale = B (1/16” Ball, 100 kgf load)

§ Brinell Load = 500 kgf

Specimen Thickness Measurement =

Specimen Hardness Measurements

Test No. / Rb / BHN Di1 / BHN Di2 / BHN Diavg / BHN (kgf/mm2)
1
2
3
4
5
6
7
8
Avg

NOTES

1. Microscope measurements for Di1 and Di2 should be done at RIGHT-ANGLES to each other

2. The quantity Diavg = [Di1 + Di2]/2

Table III – G10180 STEEL, HOT ROLLED (1018 HRS) Test Data

Hardness Scales

§ Rockwell Scale = B (1/16” Ball, 100 kgf load)

§ Brinell Load = 3000 kgf

Specimen Thickness Measurement =

Specimen Hardness Measurements

Test No. / Rb / BHN Di1 / BHN Di2 / BHN Diavg / BHN (kgf/mm2)
1
2
3
4
5
6
7
8
Avg

NOTES

1. Microscope measurements for Di1 and Di2 should be done at RIGHT-ANGLES to each other

2. The quantity Diavg = [Di1 + Di2]/2

Table IV – S30300 STAINLESS STEEL Test Data

Hardness Scales

§ Rockwell Scale = B (1/16” Ball, 100 kgf load)

§ Brinell Load = 3000 kgf

Specimen Thickness Measurement =

Specimen Hardness Measurements

Test No. / Rb / BHN Di1 / BHN Di2 / BHN Diavg / BHN (kgf/mm2)
1
2
3
4
5
6
7
8
Avg

NOTES

1. Microscope measurements for Di1 and Di2 should be done at RIGHT-ANGLES to each other

2. The quantity Diavg = [Di1 + Di2]/2

Table V – USA PENNY Coin Test Data

Hardness Scale

§ Rockwell Scale = H (1/8” Ball, 60 kgf load)

Specimen Thickness Measurement =

Specimen Hardness Measurements

Penny / Rh1 / Rh2 / Rhavg
<1982
³1982

Data Reduction Calculations

Consult the Literature and determine a “Handbook” value for the BHNs

§ List your references in Table VI below

§ TextBooks, Handbooks, technical Journals, and WebSites are Acceptable References. List your references in Table VIII.

§ Calculate the D% from the literature value as

§ D% = 100x(BHNmeas – BHNlit)/BHNlit

Estimate OTHER material properties using the Hardness values.

§ Again consult the literature (e.g., Text Fig 6.19) and use the BHN measurements to estimate for each material the:

§ ultimate tensile strength (σu or TS)

§ Enter your estimates in Table VIIbelow

§ References for the property correlations are not required, but may be appended to this report if desired.

Table VI – BHN Hardness Comparison

Specimen / BHNmeas / BHNliterature / D%
C10200 Copper
G10180 HRS
A92024-T4 Al
S30300 SS

Table VII – Property Estimation

Specimen / σu (TS) (est.)
C10200 Copper
G10180 HRS
A92024-T4 Al
S30300 SS

Table VIII – BHN REFERENCES

Specimen / Reference
C10200 Copper
G10180 HRS
A92024-T4 Al
S30300 SS

Print Date/Time = 7-Apr-08/08:03

[1] As of the latest revision (2000) of the ASTM Brinell standard E-10 the indenter must be carbide.