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Tiger Stripe Finish on Ground 304L Surface

Tiger Stripe Finish on Ground 304L Surface

Tiger Stripe Finish on Ground 304L Surface

(OP)
The band of raised material in the photo is about 1/4 inch wide, on the transverse plane of A240-304L plate. The surface has been thoroughly ground using a 240 grit sanding sleeve (alumina abrasive).
I'm wondering what has caused the pattern on the surface. I suspect it is just optical and that there is no real effect on the material, but I am looking for an expert opinion.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Tiger Stripe Finish on Ground 304L Surface

How much stock was removed?
I presume that you started with coarser abrasive and worked your way down to 240?
How thick is the plate?

Likely from some part of the plate processing and just visual.
We used to wet grind to 400 and saw weird surfaces all of the time.

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P.E. Metallurgy, consulting work welcomed

RE: Tiger Stripe Finish on Ground 304L Surface

(OP)
Thanks EdS, that's what I suspected.

Plate t is about 1.5", the strip shown is near one surface. Vintage c.1978. We did a few cycles with 80 grit to take out the worst of the irregularities, then numerous cycles of 240.
Any thoughts on the depth of work hardening or residual surface smearing? My guess is it isn't consequential.


"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

RE: Tiger Stripe Finish on Ground 304L Surface

There is a lot of sanitary service SS that is dry polished to 180 because it is good at hiding these things and making surfaces more similar.
Next time you are in St Louis visit the arch, walk up to the base and look up at it. The plate is from 3 mills and the difference in surface finish is visible. I knew a guy that could tell you which was from which mill based on the finish.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Tiger Stripe Finish on Ground 304L Surface

(OP)
Our grinding is dry, but because of the intermittent passes and large mass I don't believe it is getting very warm, but I will inquire.

Seems to me that if 180 grit dry polishing is good enough for sanitary service SS then we will have no issues. Corrosion is actually not a concern; the enclosed space just needs to stay clean in a fairly inert environment. We will be expanding a tube into this ~6"Ø bore and we need good leak tightness, so mechanical surface effects are my only concern.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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