Mechanical performance index (%)
Grade wall thickness mm elongation δ 5 ≥%% yield strength δ S (MPA ≥) test temperature ℃ Q345A ≤ 16 21 345 not required Q345B ≤16 21 345 20 Q345C 16-35 22 ≥325 0
Grade C Si Mn P S V NB Al Ti Q345A ≤0.20 ≤0.55 ≤1.70 ≤0.045 ≤0.045 0.02-0.15 0.015-0.060 0.02-0.20 Q345B ≤0.20 ≤0.55 ≤1.70 ≤0.040 ≤0.040 0.02-0.15 0.015-0.060 0.02-0.20 Q345C ≤0.20 ≤0.55 ≤1.70 ≤0.035 ≤0.035 0.02-0.15 0.015-0.060 ≥0.015 0.02-0.20Chemical composition
Mainly due to different carbon and manganese contents: Q235-A Carbon content C: 0.14 ~ 0.22; Mn: 0.30 ~ 0.65; Q235-B Carbon content C: 0.12 ~ 0.20; Mn: 0.30 ~ 0.70; It is applied to carburized or cyanide parts with low core strength requirements, such as pull rod, connecting rod, hook, bolt, shaft and weldment There should be restrictions on the temperature! Especially Q345E. Tens of degrees below zero. In addition, compared with the old standard, the most obvious requirement of the new standard is to adjust the Mn content in steel from 1.0-1.60 to ≤ 1.70, and cancel the minimum value limit of ≥ 1.0. Q345C steel pipe is one of the materials of steel pipe. Q345A, Q345B, Q345C, Q345D and Q345E are the quality grades. They increase from a to e, mainly due to the difference in impact temperature caused by different contents of micro elements such as phosphorus and sulfur, which represents the difference in impact temperature and mechanical properties of pipe chemical composition. Q345A, no impact; Q345B, 20 ° normal temperature impact; Q345C, 0 degree impact; Q345D, is - 20 degree impact; Q345E is - 40 degree impact. At different impact temperatures, the impact values are also different. Q the yield strength is not lower than 345mp, and the quality grade indicates that it contains impurity elements (carbon, manganese, silicon, sulfur and phosphorus). Is the amount of impurities (elements) in the steel. The later the A, B, C and D, the less the impurity content Q345A contains both phosphorus and sulfur less than or equal to 0.045% Q345B contains both phosphorus and sulfur less than or equal to 0.040% Q345C contains both phosphorus and sulfur less than or equal to 0.035% Q345D contains both phosphorus and sulfur less than or equal to 0.030% Q345E contains both phosphorus and sulfur less than or equal to 0.025% The more phosphorus and sulfur impurities in steel, the worse the impact toughness Q345A Q345B Akv not less than 34 at 20 ℃ At Q345C 0 ℃, Akv shall not be less than 34 Q345D - Akv not less than 34 at 20 ℃ At Q345E - 40 ℃, Akv is not less than 27 The final reason is that the reduction of P and s impurities in steel promotes the improvement of impact toughness at low temperature. One is the chemical composition of Q345 and the other is the mechanical properties of Q345Specific chemical composition of Q345C
C≤0.2%，Mn 1.0-1.6%， Si ≤0.55%, S ≤0.35%, P ≤0.35%, V 0.02-0.15%, Nb 0.015-0.06%, Ti 0.02-0.2%, AL ≥0.015% The mechanical properties are: Yield strength: ≥ 345mpa (thickness below 16mm) Tensile strength: 470-630mpa Elongation: 22% Impact energy: ≥ 34j (test temperature 0 °) 180 ° bend test: D = 2A (thickness below 16mm)The mechanical properties are
Yield strength: ≥ 345mpa (thickness below 16mm) Tensile strength: 470-630mpa Elongation: 22% Impact energy: ≥ 34j (test temperature 0 °) 180 ° bend test: D = 2A (thickness below 16mm)