49031

Crack in deep drawn components after pre treatment [India] 

June 13, 2008

Deep draw components made from CRCA 1mm thick about 5" OD and 7" height. CO2 Welding done on the outer surface, crack found after phosphating.what is the cause for this? material or drawn process or pre treatment process

Senthilkumar Ramasamy
material incharge - Chennai, Tamilnadu, India

Hi, Senthil. Phosphatizing does offer some potential for hydrogen embrittlement but I believe it's usually considered minor. Was one part cracked or all 50,000 of them? Iron phosphate ot Zinc phosphate? What is the hardness of the components? Thanks.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

What is CO2 welding?? That is a new one on me.

Welding is not amenable to deep drawing, or at least there would be problems on some if not all parts.

My thought is that anything that is deep drawn had to be fairly soft to start with. It is possible that it work hardened in the process and a stress relieve cycle may be needed. Normally it would be done at the end, but it may be needed before the start or in the middle of the steps if that were practical.

James Watts
- FL