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Black Patch problem on DOM tube surface

2003

Dear All,

We are one if the leading manufacturer of precision steel tubes in India and Exporting world wide. When we process our mother tubes ERW tubes in a pickling line after the annealing process we get black patches on the outer diameter during the cold drawing process. We use HCl acid for pickling and our annealing process is NOT bright annealing. This problem is encountered in all the tubes especially in larger dia. higher wall thick tubes. Is it due to some problem in annealing process or in pickling? We are not sure about the root cause.. Can any one help us in giving the solution?

Regards,

Sekar Kannan
Process & Development Engineer - Chennai, Tamil nadu, India

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Do you have dried or wet oil on the tube before heat treatment or the pickling process? Sounds like lead or some other metallic contamination has left its mark on the steel.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2004

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Dear Sir,

Thanks for your feedback. Actually the tubes are having coolant(very little)on their surfaces before heat treatment. Do you think this can cause such problem?

Sekar Kannan
Precision steel tubes for Auto industry - Chennai, India
2004

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Dear Mr.Sekar Kannan,

As you said may be the thickness which is not pickled properly, may I know how much concentrated is you acid and how much time you provided for your pickle process.

try give little excess time.

Deepan M
plater - Chennai, Tamilnadu, India
June 30, 2011