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Cracks found after anneal of A890-CE3MN

Cracks found after anneal of A890-CE3MN

Cracks found after anneal of A890-CE3MN

(OP)
We are a commercial heat treater. One of our customers occasionally has us anneal A890-CE3MN material. The parts have a relatively thick core (2-6"), relatively thin webbing (1/4") out to a rim with a thickness of around 1.5". Our process is heat to 2050°F, soak for a few hours (varies by section size), drop to 1910°F for 15-30 minutes, then high-pressure gas quench.

Our customer frequently finds cracks in most or all of the parts after the anneal. Sometimes they have found cracks before we ever touched the parts, too, so I'm not sure how much of the cracking is from the heat treatment and how much is just a design issue. They've also occasionally had problems with the tensile test failing. We haven't properly documented all our process history vs. their results, so I'm not sure if the tensile failures resulted from lower quench pressures that we tried or from slow heat-up rates that we tried (after some recent reading I realized the slow heat-up rate may have allowed detrimental microstructures to form).

As the heat treater, are there any changes to our process we can make to minimize the crack risk without excessively harming the tensile results? Any other non-heat treat advice we could pass on to our customer (a small cast house)?

RE: Cracks found after anneal of A890-CE3MN

"Sometimes they have found cracks before we ever touched the parts"

The cracks may already be present before you ever heat treated, but you only saw them after they oxidized and opened during heat treating. They should be examined for cracking before you heat treat. The customer has to figure out why they are cracking if they are already sending them to you that way.

RE: Cracks found after anneal of A890-CE3MN

It is truly commendable,that a small foundry is attempting . A god melt shop must be equipped with suitable refining equipments and control of Nitrogen.

Also from the part that you describe, it is a pump impeller casting perhaps . The thick core may be using a core sand that has poor collapsibility ,or the gating system must have caused a crack. Also, wrong temperature of knock out can also cause cracking.

Thus apart from design factors,foundry processing must have caused cracking. It is an issue which shall need more detailed investigation.


"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

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