Charpy Impact Testing

[midwestironman]

I am looking to prepare specimens for Charpy Impact Testing. The specimens will be made from flat rolled sheet steel (hot roll) and steel pipe.

Any and all advice regarding machining the specimens and cutting the notch is appreciated.

 

[metengr]

midwestironman;
Go to ASTM.org and see the applicable ASTM specification for impact testing of metallic materials

http://www.astm.org/index.shtml

http://www.astm.org/DATABASE.CART/HISTORICAL/E23-05.htm

 

[Tmoose]

Sor some steels Some properties are sensitive to the direction the steel was processed.

 

[unclesyd]

Adding to the sage advice post above I would check with your testing facilities about machining the specimens from the materials supplied by you. If they are setup for this it will take them no time to make and test the specimens.

It takes a little time to get the test specimens machined correctly starting from scratch. Small imperfections can cause fair size errors.

 

[EdStainless]

Let the person testing machine the samples. They are set up for it, especially broaching the notch.
Sample orientation is critical, think this through carefully and check your codes.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[redpicker]

The best method I've found utilizes a surface grinder with a magnetic chuck, a small precision vise, and a Charpy Broach (Blacks).

1) saw cut the specimens to 0.5" x 0.5" by 2.125" +0/-0.063". Be sure to mark ends so traceability of notch orientation can be maintained (Typically with a steel stamp).

2) Surface grind two sides parallel and to size (0.394" +/- 0.001")

3) Mount specimens in precision vise and mount vise on surface grinder to grind 3rd side 90 degrees to the parallel sides.

4) With 3rd side cleaned-up, grind 4th side to size (0.394" +/- .001).

5) Cut notch with broach.

Be sure to de-burr specimens after each operation. Small burrs can cause grinding errors.

Method is well suited for magnetic materials. Non-magnetic materials are difficult to hold with magnetic chuck.

The Charpy Broach is the best way to insure a good, repeatable notch. Notch quality is very important for accurate and consistant results. Charpy broach is not recommended for materials much harder than 48 HRC.

I think the ASTM tolerances are +/- 0.003" on cross-sectional dimensions, but I'd recommend working to +/- 0.001".

Steel stamp the ends prior to cutting and make sure the orientation of the stamping will allow you to put the notch on the correct side of the specimen. For some materials, notch orientation is critical.

DO NOT use vibratory engraver on (surface ground) sides for sample identification. This can cause errors in testing. Interestingly enough, a Sharpie (R) Pen does an excellent job.

rp

 

[TVP]

The following is an excellent review of Charpy testing:

http://www.msel.nist.gov/practiceguides/SP960_4.pdf

 

[deadrange]

As stated above, most outside testing labs will have the ability to machine your charpy samples. Many of them have that included in their quoted price since it is basically assumed they will be doing the machining.

Since they do it often they know what subsize they will be able to get, and do the conversion if requested. If you are trying to do it yourself on a regular basis. I would suggest investing in a CNC machine to simplify your efforts.