ASTM A213 ASME SA-213 TP347H Seamless Steel Tubes ASTM A213 ASME SA-213 TP347H Seamless Steel Tubes contains NB-Cr-Ni austenitic stainless steel. Because of the stable element Nb, it has good intergranular corrosion resistance, high endurance strength and oxidation resistance, as well as good technological properties such as bending and welding.