The alloy steel pipe firstly ensures the mechanical properties, so its trademark expresses its mechanical properties. It is indicated by Q+ number, in which the “Q” is the pinyin prefix of the yield point “Qu”, and the number indicates the yield point value. For example, Shandong Q235 round steel indicates yielding. The point is 235 MPa. If the letters are marked with letters A, B, C, and D, the quality grade of the steel is different, and the amount of S and P decreases sequentially, and the quality of the steel is improved. If the letter "F" is marked on the back of the mark, it is boiling steel, and the mark "b" is semi-killed steel, and the one not marked "F" or "b" is killed steel. For example, Q235-A·F indicates a grade A boiling steel with a yield point of 235 MPa, and Q235-c indicates a grade c killed steel with a yield point of 235 MPa.
Alloy steel pipes are generally not subjected to heat treatment, but are directly used in the supply state. Generally, Q195, Q215 and Q235 steels have low carbon mass fraction, good welding performance, good plasticity and good resistance, and have certain strength. They are often rolled into thin plates, steel bars, welded steel pipes, etc., used for construction and fabrication of general rivets for bridges, construction, etc. Screws, nuts and other parts. Q255 and Q275 steel have a slightly higher mass fraction, higher strength, better plasticity and resistance, and can be welded. Generally, rolled steel, strip steel and steel plate are used as structural members, and simple mechanical connecting rods, gears and couplings are produced. Parts, pins, etc.