The Q345 series seamless square tubes are differentiated into grades Q345A, Q345B, Q345C, Q345D, and Q345E, mainly differing in the impact temperature. Q345A grade does not require impact testing; Q345B grade is tested at 20 degrees Celsius; Q345C grade is tested at 0 degrees Celsius; Q345D grade is tested at -20 degrees Celsius; and Q345E grade is tested at -40 degrees Celsius. The impact values also vary with different impact temperatures. Within the sheet material category, it belongs to the low-alloy series. Among low-alloy materials, this type is considered standard. A previous name for the Q345 seamless square tube was 16Mn seamless square tube. Our factory can initially produce Q345 seamless and straight-seam square rectangular tubes according to customer requirements.