Cast steel porosity

jangolobow · Nov 5, 2020

Hay!

i would like to improve porosity at Cast steel CF3M. We obserev that cast steel is porouse. We would like to improve cast surface woith postprocessing. Currently we are grinding and welding the surface. Do you have some other suggestions?

We are in contact with cast steel supplier but they do not do more for the money which we pay.

Some suigestions?

Thanks

G

Tmoose · Nov 5, 2020

Got any pictures of the porosity with s steel rule in the pic for a sense of scale?

How does the porosity compare to ASTM A802 or MSS-SP-55 ?
Is the porosity just in certain areas of the part?

Do you own the pattern for the part?

Have you talked to other suppliers yet?
I'd think about the extra time it is taking to fix the porosity, add that cost to what you are paying for the castings now, and with that price in mind approach new suppliers with my ASTM A802 or MSS-SP-55 requirements and see what they would charge.

EdStainless · Nov 5, 2020

It is a lot less costly to make better castings than to fix them.
Photos are needed.

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P.E. Metallurgy, consulting work welcomed

arunmrao · Nov 5, 2020

CF3M castings, are you discussing gas porosity or shrinkage porosity. The two are distinctly different. A picture will describe a hundred words.

jangolobow · Nov 6, 2020

Hay!

I am attachning the picture. Is difficult to take a photo on relative small pores.

First photo is under normal white light and the same area under UV light.

Pores are randomljy distrubuted all over the casting part.

For me it looks like some dirt however it is empty - hole.

I do not know which type of pore it is. Our supplier does not tell us much about his process and his problems at process. Any input is welcome!

J

jangolobow · Nov 6, 2020

And photo under UV light

jangolobow · Nov 6, 2020

Photo normal light

bobjustbob · Nov 9, 2020

It is tough to diagnose a casting problem like this with just some up close photos that don't have anything for scale or location.

Are you seeing the indication all over the part or in one area?
Is it showing in one particular part number but not in others?
If it is randomly dispersed in multiple parts in multiple locations then that indicates more of an issue with the molten metal and you need to look at the melting, pouring and deoxidation practice for that material.

If it is showing up in one location in a particular part, you want to look at what in the configuration of that pattern could be causing the problem.
Is it showing up under a head contact or dirt trap?
Is it showing in the cope uppermost flange?
Is it next to a thin section that is freezing off?
Is it under a chill or vent?

To do a proper diagnosis you need to look at the pattern and the part with the indication locations to determine where the problem lies.

Bob

mrfailure · Nov 9, 2020

First step is to identify type of porosity using metallographic analysis. If you cannot sacrifice a casting or remove a boat sample, then you can try identifying using replication.

arunmrao · Nov 9, 2020

Maybe, they can refer to the excellent publications from AFS on Defects in Castings. I am certain, it will help in getting to the root cause.I agree with Bob's observations.

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Cast steel porosity

jangolobow

Chemical

Tmoose

Mechanical

EdStainless

Materials

arunmrao

Materials

jangolobow

Chemical

jangolobow

Chemical

jangolobow

Chemical

bobjustbob

Materials

mrfailure

Materials

arunmrao

Materials

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