A variety of classification methods exist. By manufacturing process, they are categorized into hot-rolled seamless pipes and cold-rolled seamless pipes. By application, they include general structural seamless steel tubes, fluid conveyance seamless steel tubes, medium and low-pressure boiler seamless steel tubes, high-pressure boiler seamless steel tubes. Material-wise, they are carbon structural steel seamless steel tubes, low-alloy structural steel seamless steel tubes, and alloy steel seamless steel tubes. Seamless steel tubes have a wide range of uses, such as manufacturing mechanical parts, conveying liquids or gases, serving as drive bearings, and constructing rigid structural buildings.

The external standard for Q345B seamless steel tubes is GB709, and the internal standard is GB/T1591-94.

Similar to the naming method of Q345B.

Due to execution standards, this steel plate allows for negative tolerance delivery.

Q345 seamless steel pipe is a type of steel pipe material. "Q" signifies the yield of this material, and the following "345" indicates the yield strength, which is around 345. It decreases as the thickness of the material increases.