HDG steel pipe 1. many different sizes of the products 2..low and ... production process are made under the ISO:9001-2000 strictly1) Standard:API 5L,ASTM 36.10M,A106,A53,DIN 1629,1626 ... , XS, XXS etc.6) Technique:Hot Rolled,Cold Drawn,Seamless,ERW,LSAW,SSAW,7) Surface treatment:bare,black painting,anti rust ... ,gas,chemical,power,shipbuilding,boiler,construction,,metallurgy,etc HDG steel pipe