Good morning, all. I am trying to find a standard that governs ANSI swivel type flanges. At our shop we make these, but for some reason we make the bullet part out of carbon steel such as A105 and the donut/ring out of 4130. I cannot for the life of me figure out why we are doing this and QC has been no help. I have been told that is what was always done. No one can give me a reason as to why. I was trying to find some information so I can convince them to use A105 on the ring part to save money in materials and welding consumables. Any help would be appreciated.