I am currently in the process of evalauting aluminum 6061-T6 and 6063-T6 extruded samples from a supplier in China. I am having a difficult time determining the hardness. Does anyone know of a good conversion chart for hardness. (rockwell B, vickers, brinell)?
The test reports I have received specifiy HV 70. When testing them I get a Rockwell B value of 24

Thanks,
Phil

Hope this helps.

http://www.carbidedepot.com/formulas-hardness.htm

For the "official" information, get a copy of ASTM E140, Standard Hardness Conversion Table for Metals, Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness and Scleroscope Hardness. Available from www.ASTM.org - if you want it in a hurry and have a credit card, you can charge the card and get a pdf download.

Many manufactures of hardness testing equipment will also supply charts free of charge to existing customers - try Wilson Instruments, or whoever manufactured or calibrates your hardness testing equipment

Phil,

The closest E-140 has is a chart for "Wrought Aluminum Products".

In it, your HRB 24 is off the chart ( the lowest HRB value listed is HRB28 which converts to HV80 (15Kg).

If you can test on HRE scale (1/8" ball) HV70 is approx HRE71.

Brinell(500Kg, 10mm) looks to be about 61 or so.

If you'd like a wall conversion chart, get ahold of me at
optical_service@leco.com with a mailing address and
I'll have one sent. Unfortunately, it will be for non-austenitic steels, not aluminum. :(

tim

I checked my conversion chart from Wison Instruments and it does not show any conversion from the B scale to HV. You might want to call them and find out what they would do with aluminum. It has been my understanding that with aluminum there is no real reliable B scale rockwelling that can be done. Might want to check with an aluminum producer to see what they do.

There may be a chart that shows comparative values in ASTM E 18.....I won't swear to it, but check there. E 18 is the calibration/check standard for hardness.

Hershal

As mentioned above, conversion charts are in ASTM E-140.

There are several different charts for different materials.

I’m getting the feeling that unless you have a “official” conversion chart; the ones that are free online are no good? :confused:

How about this one? http://www.gordonengland.co.uk/hardness/hardness_conversion_3c.htm

Cordon - my experience in running a materials testing lab, and a short stint years ago as a field engineer for engineering studies of process equipment reinforced that you always want to be able to fall back to knowing where the numbers come from - ideally basing them on a primary reference such as ASTM standards, SAE specifications, etc. If you've followed the standard/specification the numbers you generate can be defended - if not, you're always open to someone who has followed them.

The ones posted online may be fine - but how do you know they are - someone could have made a mistake in developing the numbers posted. I would use them as a reference, but would go back to a primary source such as the standards to check them.

Regarding Hardness - based on notes above you may need to do some sort of double conversion - Rockwell B to Rockwell H, and then H to vickers, or vice versa. When you do a double conversion, the numbers get a lttle "fuzzier", because each conversion is only approximate.

I am currently in the process of evalauting aluminum 6061-T6 and 6063-T6 extruded samples from a supplier in China. I am having a difficult time determining the hardness. Does anyone know of a good conversion chart for hardness. (rockwell B, vickers, brinell)?
The test reports I have received specifiy HV 70. When testing them I get a Rockwell B value of 24

Thanks,
Phil

There's been some very good advice in this thread so far, but I thought I would add another alternative, which would be to have the samples tested by an independent source. I think this is especially important when qualifying a far-away supplier, and might not be all that expensive when compared to the potential for bad things to happen. If you're not sure about your results--and conversions between different scales is a slippery slope--you're going to need independent evaluation if a dispute arises. Independent testing will tell you two things--whether the samples meet the standards, and whether or not your supplier's report is accurate.

I’m getting the feeling that unless you have a “official” conversion chart; the ones that are free online are no good? :confused:

How about this one? http://www.gordonengland.co.uk/hardness/hardness_conversion_3c.htm

Even "official" conversion charts are not gospel. Quoting E-140, 1.12 here:

"The conversion values, whether from the tables or calculated from the equations, are only approximate and may be inaccurate for specific applications".

Most folks seem to have, and use, variations of Table 1 in E-140. The first problem that comes up is that the material being tested may not be that for which the table is intended, in this case Non-Austenitic Steels.

Other problems are the ignoring of the column headings. For example, the Knoop column specifies 500 gram loads or
greater, yet the facility will be testing at 200 grams.

Another is with the Vickers column. That column is referring to the English Vickers Test (known as Macro or Heavy Load Vickers in the US), and a load of 10 Kg. Many facilities using microindentation testers and Vickers indenters will use this column for their conversions.

The problem with the two examples above is that the test results are "Load Dependent" at lesser loads than those specified, i.e. if you test a part with 50 gm Knoop and 300 gm Knoop loads, the 50 gm result will always tend to give a higher Knoop number.

The only reliable way to determine the conversion factors for your particular application is to actually do the testing on the different scales. You then develop a "reliable basis for the conversion" for your material.

There are nine tables given in E-140. Make sure you pick the one that closest matches your material, and then take the numbers with a grain of salt.

Or better yet, do the actual testing (or have it done outside) on the different scales and develop the
conversion data. Then YOU know that you are RIGHT.

(True, scarey story: Cust A tests at 200gm Knoop and converts to HRC, wrongly. Cust B tests at 500gm Knoop and converts to HRC, correctly within the constraints of conversions) Cust B notices that parts from Cust A are testing lower upon receipt than A specified. A + B meet to discuss. Result of discussion is that Cust B changes their method to match that of Cust A. Parts are now actually coming in softer than specified, but A + B are now getting the same (wrong) result so they are happy!

The parts go in aircraft engines.:mg:

Thank you to all that have replied. I think I have enough enough information now to go to my engineering dept to discuss the next step in our evalaution.
NOTE: I also sampled our current production and received the same Rockwell B numbers. We have no issues with these parts, we use two of these parts to hang a steel door approximate size 3' x 5'.

Phil:thanks: