"Cold" Service Metal welded to "Normal" Service Metal 1

[Brandon181]

I have a small piece of "in-line" equipment made up of a cylinder and flange on each end. The cylinder was specced as SA-333 Gr. 6 (min temp -50F at my thickness by B16.5). The flanges were specced at A-105 (min temp -20F by B16.5). The MDMT for this project is -20F. I have two questions:

1. Why would the vendor quote SA-333 Gr. 6 when SA-106 Gr B. would have been acceptable for my thickness? I would think that it would be more expensive to produce SA-333 Gr. 6 but perhaps this is a misconception. I have noticed many vendors quoting SA-333 Gr. 6 for pipe that is not in low temperature service.

2. Are there any problems welding a SA-333 Gr. 6 ("low" temp) to a A-105 ("normal" temp) flange? I assume they have the same carbon content so there should be no issues but I am not very versed in welding.

Any help would be appreciated! Thanks in advance.

 

[metengr]

Probably the use of a A333 Grade 6 was readily available versus A 106. Also, A 106 is seamless carbon steel pipe specified for elevated temperature service. There should be no weldabilty issues or concerns with the stated materials. Follow proper preheat requirements and maintenance.