Charpy testing CD4MCuN castings
Charpy testing CD4MCuN castings
(OP)
I am looking for the causes of low Charpy test results for ASTM A995 gr 1B (CD4MCuN) castings. All other mechanical & metallurgical results meets requirements but the Charpy results are 50% below the acceptance criteria. I know the problem is in heat treat (SA + WQ) but I am not exactly sure where.
Any help would be greatly appreciated.
foundry1
Any help would be greatly appreciated.
foundry1





RE: Charpy testing CD4MCuN castings
The first thing to look at would be your SA time and temperature, test block section thickness, and transfer time from the H/T oven to the quench. Is your quench tank big enough for the amount of metal being put in it? Is your charpy test temperature correct and not too low?
RE: Charpy testing CD4MCuN castings
Temperature is -10C.
There were 4 heats sampled. The following chart displays the mechanical results along with the average of each charpy tests.
HRB YIELD TEN. ELONG RA AVG CHPY
REQ'D >28 70 100 16 36-45
HEAT #
BCBA 24 71.4 111 37 55.6 136
BDBA 27 72.6 111 31 49.4 30
BEBA 23 70.3 113 34 50.6 27.7
CCBA 23 72.4 112 32 50.7 24.3
I do not have all the answers to your questions but intend to find that out.
Thank you for your response. I look forward to any further input you might have.
foundry1
RE: Charpy testing CD4MCuN castings
I would strongly suggest you or have a met lab perform metallographic examination of the suspect CVN impact test failures and evaluate their microstructure. This can be easily done on one of the fractured CVN impact pieces, and use the other piece for SEM evaluation (if rquired). You may find your smoking gun.
RE: Charpy testing CD4MCuN castings
RE: Charpy testing CD4MCuN castings
Thanks for your response. I've discovered that three of these heats had slightly elevated carbons, max C was .047. What bearing could this have on these Charpy results or the microstructure?
Foundry1
RE: Charpy testing CD4MCuN castings
Not much effect for this difference (0.040% versus 0.047% by mass). What is the nitrogen content, and more important did you have the lab analysis done as recommended above?
RE: Charpy testing CD4MCuN castings
I know a group at ASTM that would really like any data that you generate on this.
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Plymouth Tube
RE: Charpy testing CD4MCuN castings
Here is a tip, visit the web page below, scroll to the bottom of the page and download the document titled "Practical Guidelines for the Fabrication of Duplex Stainless Steels." It is an excellent technical reference document if you will be dealing with duplex stainless steels on a regular basis, and is free.
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RE: Charpy testing CD4MCuN castings
"Ferite-point count conforms, Exhibits 45.27%* ferrite.
Etch/Mag: ASTM #80/100,200,500X"
"Microstructure conforms, Free from intermetallic phases and precipitates. Etch/Mag: ASTM #80/100,200,500x"
*These ferrite percentages range from 45.27 to 46.77% for the four heats.
My customer has had to reject these castings based on the Charpy results. My concern is that if I remake them I will follow exactly the same procedures and practices that produced these rejected castings. I think the lab made a mistake in the Charpy tests but have no way to prove it and no way to guarantee that they will not do it again.
Any Recommendations?
Foundry1
RE: Charpy testing CD4MCuN castings
RE: Charpy testing CD4MCuN castings
RE: Charpy testing CD4MCuN castings
It is sad that you do not have additional test piece to offer. The only recourse is now to produce a heat (hope it is economical and sensible) undr exactly similar conditions and have some additional test bars processed.
It is not recommended to draw samples from castings as they may not be sound.
I always make a separate test check and then offer test bars to the customer. this is expensive,but you are confident and can foresee,if there are any issues involved before making an offer
You mentioned that all tests conform to the standards,but the impact results are suspect . Next time arrange a witness test and also involve the customer in this program. This will strengthen his confidence in your casting and any minor deviations can be condoned.
It is my experience that carbon plays an important role in imact test values. 0.07% is a big margin,I would be more comfortable with lower carbon.
Can you also check the route that you have issued for making the charge. Are there any issues of tramp elements showing up?
I have not failed. I've just found 10,000 ways that won't work." — Thomas Edison
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RE: Charpy testing CD4MCuN castings
RE: Charpy testing CD4MCuN castings
Foundry1