Q345 welded steel pipe is a kind of low alloy steel (C < 0.2%). It has good comprehensive performance, good low temperature performance, cold stamping performance, good welding performance and machinability. Q345 Welded Steel Pipe is widely used in bridges, vehicles, ships, buildings, pressure vessels, etc. Q stands for the yield of Q345 steel. The later 345 is the yield value of Q345 material, which is about 345 MPa. The yield value decreases with the increase of material thickness.
The naming method of Q345 welded steel pipe is similar to Q235. The Q345 steel covers steel grades Q345A, Q345B, Q345C, Q345D, Q345E. This is the grade distinction, which mainly represents the different impact temperatures. Q345A, no impact; Q345B, 20 degree normal temperature impact; Q345C, 0 degree impact; Q345D, -20 degree impact; Q345E, -40 degree impact. At different impact temperatures, the impact values are also different.
Chemical composition of Q345 welded steel pipe:
| Grade | C | Si | Mn | P | S | V | Nb | Al |
| Q345A | 0.20 | ≤0.55 | ≤1.70 | ≤0.045 | ≤0.045 | 0.02-0.15 | 0.015-0.060 | - |
| Q345B | ≤0.20 | ≤0.55 | ≤1.70 | ≤0.040 | 0.040 | 0.02-0.15 | 0.015-0.060 | - |
| Q345C | ≤0.20 | ≤0.55 | ≤1.70 | ≤0.035 | ≤0.035 | 0.02-0.15 | 0.015-0.060 | ≥0.015 |
| Q345D | 0.18 | ≤0.55 | ≤1.80 | ≤0.030 | ≤0.030 | 0.02-0.15 | 0.015-0.060 | ≥0.015 |
| Q345E | ≤0.18 | ≤0.55 | ≤1.80 | ≤0.025 | ≤0.025 | 0.02-0.15 | 0.015-0.060 | ≥0.015 |
Mechanical property of Q345 welded steel pipe:
Yield strength: <16mm: greater than 345Mpa, 16-40mm: greater than 335Mpa, 40-63mm: greater than 325Mpa, 63-80mm: greater than 315Mpa,
80-100m: greater than 305Mpa, 100-150 mm: greater than 285Mpa, 150-200 mm: greater than 275Mpa.
Tensile strength: 450 - 630Mpa.
Elongation: greater than 17%.