Thread Content
Chemical composition (melting analysis): 1. Carbon steel and low-alloy steel used for welding: C≤0.25%, P≤0.035%, S≤0.035% [2.2.1.2.1 in TSG21-2016]. 2. Carbon steel and low-alloy steel intended for use in pressure vessels must meet the following requirements: [2.2.1.2.2 in TSG21-2016]. Note: The following refer to specialized steels: GBT 713-2014 – Steel plates for boilers and pressure vessels; GBT 3531-2014 – Steel plates for low-temperature pressure vessels; GB 19189-2011 – Quenched and tempered high-strength steel plates for pressure vessels; GBT 9948-2013 – Seamless steel tubes for petroleum cracking; NBT 47008-2017 – Forged carbon steel and low-alloy steel components for pressure-bearing equipment; NBT 47009-2017 – Forged low-alloy steel components for low-temperature pressure-bearing equipment; NBT 47010-2017 – Forged stainless steel and heat-resistant steel components for pressure-bearing equipment. (1) For steels with a minimum standard tensile strength of ≤540 MPa, P≤0.030% and S≤0.020%； (2) For steels with a minimum standard tensile strength of >540 MPa, P≤0.025% and S≤0.015% ； (3) For steel designed for temperatures below -20°C with a minimum standard tensile strength of ≤540 MPa, P≤0.025% and S≤0.012% ； (4) For steel designed for temperatures below -20°C with a minimum standard tensile strength > 540 MPa, P ≤ 0.020% and S ≤ 0.010%. Mechanical properties – Impact energy criterion: 1. For the following materials, the impact energy (in kv) for V-notched specimens at the impact test temperature specified in the design requirements must comply with the values given in Table 2-1. [2.2.1.3.1 in TSG21-2016] (1) Steel plates with a thickness of not less than 6 mm ； (2) Steel pipes with diameters and thicknesses that allow for the production of small-scale impact specimens with a width of 5 mm ； (3) Steel forgings of any size ； Note 2-1: (1) The sampling location and direction of the specimen shall comply with the provisions of the relevant steel standards ； 2) For the impact test, 3 standard specimens (with a width of 10 mm) are taken per group. It is allowed for the impact energy value of 1 specimen to be lower than the value listed in the table, but it must not be lower than 70% of that listed value ； (3) When the dimensions of the steel make it impossible to prepare standard specimens, small impact specimens with widths of 7.5 mm and 5 mm should be prepared in sequence; their impact energy values shall be 75% and 50% of those of the standard specimens, respectively ； (4) Steel grades with impact energy values higher than those specified in Table 2-1 must also comply with the requirements of the corresponding steel standards. Definition: Lateral expansion amount – the increase in lateral expansion on both sides of the back of the impact specimen due to the impact force applied during the impact test; a value of LE greater than or equal to 0.53 mm is taken from the ASME standard values. Mechanical properties – Elongation after fracture [2.2.1.3.2 in TSG21-2016]: 1. The elongation after fracture of steel plates, steel pipes, and steel forgings used as pressure vessel components shall comply with the provisions of this regulation as well as those of the relevant steel standards ； 2. For carbon steel, low-alloy high-strength steel, and low-alloy low-temperature steel plates used in welded structures, the elongation after fracture value shall meet the requirements specified in Table 2-2 ； For Image 3, the elongation values of specimens of different sizes shall be converted in accordance with GB/T 17600.1 \"Conversion of elongation for steel – Part 1: Carbon steels and low-alloy steels\" and GB/T 17600.2 \"Conversion of elongation for steel – Part 2: Austenitic steels\"; the resulting values shall meet the requirements specified in this clause ；