ASTM A312 TP321H HFW Solid Finned Tube with 11-13Cr Fins For Process Furnaces ASTM A312 TP321H HFW Solid Finned Tube with 11-13Cr Fins is a high-performance, composite tube designed for efficient heat transfer in high-temperature and corrosive environments. It consists of a core pipe made of a special stainless steel (TP321H) with fins made of a heat-resistant chromium steel (11-13% Cr) welded onto its outer surface. The "HFW" and "Solid" describe the manufacturing process of