Cracking in C276 Casting
Cracking in C276 Casting
(OP)
We are attempting to repair a 1/2" thick C276 cast cylinder ~ 4' diameter x 6' long. It has seen temperature cycles from ambient to ~ 1400F and operates in a low PH environment.
We received it with a rather large crack about halfway down the length and running about half way around the circumference. When we attempt to weld it, the parent metal cracks 1/2" - 1 1/2" away from our repair. We tried using SMAW with minimum heat input and running beads about 2" long in different areas, allowing them to cool, but, the parent metal cracked on the other side. In other words we were welding on the OD of the part and it cracked on the ID.
Any ideas?
We received it with a rather large crack about halfway down the length and running about half way around the circumference. When we attempt to weld it, the parent metal cracks 1/2" - 1 1/2" away from our repair. We tried using SMAW with minimum heat input and running beads about 2" long in different areas, allowing them to cool, but, the parent metal cracked on the other side. In other words we were welding on the OD of the part and it cracked on the ID.
Any ideas?





RE: Cracking in C276 Casting
Have you verified the chemical composition of the casting as being C276?
RE: Cracking in C276 Casting
I'll let you know the results from that.
I'm wondering if C 276 in the service described above could be expected to fatigue.
The main crack is about 5' long and the owner says there is a door on the unit at that location, which is opened regularly, and so that area on the cylinder sees a rapid temperature drop.
RE: Cracking in C276 Casting
I would be more concerned that the casting was either not properly solution treated or you have contaminants on the ID surface of the cast cylinder. The C-276 material exhibits excellent weldability using GTAW and SMAW processes. If the chemical composition meets the requirements for C-276, I would look to an improper solution anneal heat treatment from day one or some type of surface contaminants. Can you extract a small boat sample containing the ID crack and send it out for metallurgical analysis? This would confirm alloy ID, identify the nature of the ID crack, and provide information as to the alloy microstructure.
RE: Cracking in C276 Casting
Could you clear up a little information in you first post.
You state that it sees a temperature swing of 1400°F and then you state that the crack was in the casting as received.
Is this new casting or an in service casting?
If in service high often is the heat cycle and the times at temperature?
RE: Cracking in C276 Casting
Unclesyd, this casting has been in service, to the best of my knowledge, a year or so. We used to fabricate this part for them, out of C276 plate, and they would last about a year, so, several years ago they went to a casting, and they say that has extended the life of the part to around 18 months.
I'll have to ask them for more specific info re: times at temp.
RE: Cracking in C276 Casting
I don't want to get to far ahead and lead you down the wrong path, but the more I think about your situation the more you need to remove a material sample with a crack for better diagnosis (if the chemistry confirms correct material). This analysis can be turned around quickly and will provide information regarding permanent repairs. Good Luck
RE: Cracking in C276 Casting
RE: Cracking in C276 Casting
RE: Cracking in C276 Casting
What is the acid? Much F in the application?
But, I tend to believe that my senior brothers hit this one, that this part may have some more fundamental problems. Like composition and microstructure.
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RE: Cracking in C276 Casting
RE: Cracking in C276 Casting
Microstructural analysis of the sample will provide a some much needed information.
Are there any very small cracks on the OD of the casting besides the large crack?
What type casting is the shell?
I'm trying to find some old brochures on Hastelloy 276 where they talked about C276. If I recall one of the benefits of the C276 material was the improvement in weldability over 276.
RE: Cracking in C276 Casting
Brochures of C-276 are not going to help you much, because structure and purity of the rolled material can not compared to the as cast material.
The quality of the cast c-276 depends on purity of the metal and most important carbon content, as low 0.015 or lower!
It goes a bit to far to go deep into this matter, but I am afraid that your casting maybe is in the spec of c-276 castings but full is with impurities and has on top of that a high carbon content.