Decarburization of T11 HX Tube

[Guest102023]

I am examining a 3/4" diam tube, fairly heavy wall. I see about 0.008" decarb on the outside (boiler water) but none on the ID (hydrocarbons with some H2).

The structure looks well cooked from the original heat treatment, and service temp was not high enough to alter it. Hardness is about 160HV.
Is this uneven decarb a common manufacturing condition?

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[metengr]

In production of hot finished boiler tubing, decarb can be on the OD and ID surfaces or either from what I have seen over the years - it depended on the mill and tube manufacture. Suggest you review the article below for information;

http://journals.cambridge.org/actio...22&jid=MAM&volumeId=11&issueId=S02&aid=326921

 

[Guest102023]

Thanks metengr,
I found a takeaway of uneven decarburization caused by annealing, in spite of the puzzling write-up.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"