I noticed that the Carbon max requirements are different for X65 vs X56. X65 max is .12 while X56 is .22. How much carbon must be added in order to see a significant change in yield strength?
The information we have is that yields at the steel mill were in the 70-75 ksi range and we are now seeing between 60-65 ksi once pipe is formed. The steel mill numbers are average and not higher or lower than we would expect . This is API 5L X65 material. We haven't seen test data from steel...
We are having considerable drop in yield strength once we have steel coil formed into pipe. We are seeing average drop of 15-18 ksi, where normally only 2-5 ksi is expected. Without having seen steel mill test data, what could be causing such drop in yield???
I have looked in our company specs and API 1104 but can't find any requirements on wait time before a production weld on pipeline should be x-rayed. Are there any guidelines for this?
