500 mpa astm a53 welding carbon steel plate. what is structural gb t 4171 q235nh weather corten plate. About Us. FRD is an exporter of steel supply. We have our own steel pipe factory, advanced processing equipment and excellent team. We have extensive experience in exporting, and we have customers all over the world who purchase steel products ASTM A500-Cold-Formed Welded and Seamless Carbon ASTM A500 covers cold-formed welding and seamless carbon steel tubes for welding of bridges and buildings, riveted or bolted structures, and round, square, rectangular, or special-shaped steel tubes for general structural purposes. ASTM A500 steels have a density of approximately 7850 kg/m3 (0.284 pounds per cubic inch).