Large variation in Charpy impact test results

[rbrez]

Without going into detail, is it normal for a high tensile steel (over 80,000 psi) to have a large variation of charpy impact test results of, ie - 10 to 120 ft-lbs?

 

[metengr]

No, not this wide range of variation.

 

[metengr]

Just to add, the strength of the steel is related to carbon content - as the carbon content increases so does the strength. Typically, for the Charpy impact test data that I have seen, as the carbon content increases the Charpy impact curves will tend to flatten out ( develop less spread between upper and lower shelf impact energies as a function of test temperature extremes) in comparison to steels containing lower carbon contents.

Of course, there are exceptions to the above because of heat treatment effects. However, since you did not get into any detail, the above post is a general observation.

 

[SJones]

The test temperature isn't stated. Appreciable scatter will be exhibited in the ductile-brittle transition region. Where that region is depends upon the specific material (including processing route & parameters) and the temperature.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[stanweld]

Chemistry, melting practice and thermal-mechanical treatments all have significant effect on toughness properties at a given temperature or temperature range with steels having equivalent tensile properties.

 

[EdStainless]

If you are having trouble isolating variables you may want to rough machine a set a bars and then re-heat treat them. After that you can finish machine them and test.
With stronger materials slight differences in the machining of the bars can also have a big effect.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[arunmrao]

Are the samples drawn from the same batch? Also were the test pieces prepared at the same facility? How about the location of the sample drawn from the metal.

 

[redpicker]

In referring to 80,000 PSI tensile strength steel as "high strength", my guess is that the heat treat condition is other than quench and tempered. If the heat treat condition is not specified, and the difference between CVN values you mention is between different lots, then I would not be suprised by this difference.

It almost sounds like what a steel mill might quote when pressed for what CVN values they would expect with hot rolled product. As mentioned above, even within a lot, depending on chemistry and heat treatment (as well as test temperature), the CVN results can vary widely. Of course, this is why these variables are closely controlled for applications where the CVN values are critical.