superduplex craking during water cooling
superduplex craking during water cooling
(OP)
I have diametral internal craking problems (big internal cracks) in superduplex round bars during water cooling. Of course, above all in big sizes.
Which is the best option to avoid this defect?
I would like to eliminate a post solution annealing after cooling on air.
Which is the best option to avoid this defect?
I would like to eliminate a post solution annealing after cooling on air.





RE: superduplex craking during water cooling
You need to provide background information on the above problem to receive useful tips. What was the processing history of the bars? Can you provide a picture of the internal cracking?
RE: superduplex craking during water cooling
This is tipical after rolling and quench in water. The temperature of the bars before quenching is over 900º C.
The bars are formed in two rolling steps, coming from ingot. The heting temperature before rolling is over 1250º C. The rolling temperature is over 1000º C.
RE: superduplex craking during water cooling
However, if you are sure internal cracking is not caused by a wrong preheating process (i.e cracking before quenching ), the reason why large round bars fails is due to a premature coming out of the water quenching tank. These grades must be cooled until room temperature before come out of the tank.
Waiting for more info....
RE: superduplex craking during water cooling
Annealing temperature is too low for these grades: intermetallic phase could exist also on surface, not only in the core.
This cracks is typical of not complete cooling as I mentioned in my previous post. You must wait for before come out from water.
RE: superduplex craking during water cooling
Because of their thermal conductivity there will be thick sizes that are impossible to quench enough to suppress intermetallic formation.
You have to quench these until all of the material is below 300C
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Plymouth Tube
RE: superduplex craking during water cooling
RE: superduplex craking during water cooling
And one more thing, make sure that the cracks are from quench and not actually hot cracks from your forging. I am a little skeptical.
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Plymouth Tube