Charpy Impact Testing
Charpy Impact Testing
(OP)
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.
Any and all advice regarding machining the specimens and cutting the notch is appreciated.





RE: Charpy Impact Testing
Go to ASTM.org and see the applicable ASTM specification for impact testing of metallic materials
http://www.astm.org/index.shtml
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RE: Charpy Impact Testing
RE: Charpy Impact Testing
It takes a little time to get the test specimens machined correctly starting from scratch. Small imperfections can cause fair size errors.
RE: Charpy Impact Testing
Sample orientation is critical, think this through carefully and check your codes.
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Plymouth Tube
RE: Charpy Impact Testing
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
RE: Charpy Impact Testing
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RE: Charpy Impact Testing
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.