Letter 30028

Cleaning Of Stainless Steel 304 [India]  

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We need to deep draw SS-304 bowls to a depth of 116 mm. Due to the irregular shape of this bowl we need to deep draw the piece up to 70 mm and then we put it in the oven at a temperature of 800 degrees Celsius before doing the balance required deep drawing. This way we avoid the wrinkles. Now the problem is that the bowl becomes completely black once it comes out of the oven. We need to get rid of this blackness as we have to polish this piece. Can you please help us ?

Rishi Dewan
sheet metal components manufacturer - Ghaziabad, Uttar Pradesh, India

You can use next solution:

65 gm iron-III-sulphate
1 lit 2% HF
20-60 C temp. or: 66% water
15-25 %phosphoric acid(conc.)
2-4% nitric acid(conc.)
2-5% hydrochloric acid(conc.)
75-100 C temp.

Goran Budija
- Zagreb, Croatia

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