Ted Mooney, P.E. RET
- Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Stress relieving of stainless steel deep drawn products
Q. Guidance required for a solution to cracking on very deep drawn stainless steel parts. Stress relieving of the product to be done in what manner?
The product tends to crack after a few minutes/hours or sometimes weeks after been deep drawn. The product is a large size bowl measuring 20" x 16" x 12" deep made out of 1 mm thickness stainless steel sheet of grade AISI304-18/8.
I tried heating the piece and it works, but not all the time. Please guide me as to what is the right process to make the sheet soft and stress-free after deep drawing.
- New Delhi, India
A. Make sure that you do the heat treatment at a temperature that is elevated enough (1050 °C), otherwise you risk the formation of a sigma phase with detrimental effects on the properties. For the same reason, the cooling rate also becomes important.
Kind regards,
- Belgium
A. Depending on the final shape of your component, it is possible to almost eliminate the residual stresses in your product by optimizing the profile of the draw die. Maybe you can save the annealing process - and save lots of money! Many companies working in stainless steels could. The right choice of die geometry requires an analysis of the specific product.
Mortensen [surname deleted for privacy by Editor]- Aalborg, Denmark
A. Why do you want to heat a 1 mm stainless steel bowl once it has been cold formed? I agree with the comments from Mortensen, but I would polish the bowl to check if cracks are visible straight after deep drawing; the cracks may be due to surface roughness of the sheet metal.
West [surname deleted for privacy by Editor]- Deutschland
January 15, 2008
Q. Dear: Sir
My customer in Belgium produced the tea pot by using stainless 304 and faced problem of delayed cracking after drawing about 20 min.
He pointed that the cause of this problem came from the carbon content; he informed that no problem when carbon was not over 0.04% but had problem when the carbon about 0.06%.
If we consider the surface roughness, I would like to know;
How does the surface roughness result in the delayed cracking problem?
Thank you in advance for you advice!
Wichai
customer technical service - Thailand
A. Inter-stage stress relieving, and finishing of die, is important on finished products to keep dimensions intact. Experience has shown that ultrasonic cleaning process helps significantly.
AJAY SONI- Admedabad, Gujarat, India
June 30, 2008
Q. We introduced a stainless casing, drawn from 304 stainless, which will be used in mining of South Africa. Actually we have some samples there. Now we found the corners of the drawn parts have cracks in 1 month after it is being used under the mine. We are looking for all resources to look into this problem. But we are still confused till now.
Can someone know more about this and contact me(Aaron at Linde group)
Thanks,
- Shanghai, China
December 6, 2013
Q. We were deep drawing a ss pot of approx. 8" dia and 4.75" of deep in 202 grade and on the same die we draw of 304 grade also of same thickness. Every thing was ok. Later we bulged both pots of different grades -- unexpectedly no piece of 204 grade got cracked from top edge but 14% of 304 grade pots got cracked. What may be the reason.
Rahul jainmetals - Moradabad,Uttar pradesh, India
June 9, 2014
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Ed. note: We're happy to post your inquiry, Aaron and Rahul, and to post any responses. But this site focuses on metal finishing, and that is the only area of expertise of the site operators -- so we can't help you personally.
Heat treatment temperature for 202SS
Q. Up to what temperature should SS202 samples can be heated during heat treatment and what is the procedure for heat treatment for the corrosion studies experiments?
Ravali Pinnaka- Warangal, Telangana, India
November 9, 2015
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