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Thick pipes: Some requirements for thicker pipes are as follows: 01 For steel pipes with a wall thickness greater than 30 mm, it is not allowed to use hot rolling at a final rolling temperature that corresponds to the normalizing temperature as a substitute for normalizing treatment. 02 When the wall thickness of the take over is greater than 10 mm, steel pipes of grades 10, 20, and Q345D as specified in GB/T 8163 shall not be used. 03 For 10 and 20 grade steel pipes specified in GB 9948, with an outer diameter of not less than 70 mm and a wall thickness of not less than 6.5 mm, impact tests at -20°C and 0°C shall be conducted respectively. The average impact energy of the three longitudinal standard specimens shall be not less than (31 J–GB150) / (40 J–GB9948), and the minimum value for any one specimen shall be not less than 22 J (28 J). The impact energy requirements for smaller-sized specimens are in accordance with the provisions of 3.8.2. Requirements for thicker forgings are as follows: 01 Cylindrical, annular, and bowl-shaped forgings used as vessel shells and heads shall be of Grade III or IV. 02 Low-alloy steel forgings with a nominal thickness greater than 300 mm shall use grade III or grade IV. 03 Low-alloy steel forgings with a nominal thickness greater than 200 mm and an Rm ≥ 540 MPa shall use grade III or grade IV. 04 Low-temperature steel forgings with a nominal thickness greater than 200 mm shall use grade III or grade IV. 05 For manholes, forgings shall be of grade III or IV.