① Implementation standards of Q345D seamless steel pipes: GB/T8162 seamless steel pipes for structures, GB/T8163 seamless steel pipes for conveying fluids, GB/T6479 seamless steel pipes for high-pressure and high-pressure fertilizer equipment, except GB/T8162 seamless steel pipes for structures, GB/T8163 and GB/T6479 should comply with the requirements of the pressure pipeline type test rules
② Chemical composition of Q345D seamless steel pipes: carbon: 0.12~0.18, silicon 0.20~0.50, manganese: 1.2~1.7, chromium: ≤0.30, vanadium: ≤0.15, niobium: ≤0.07, nickel: ≤0.50, phosphorus: not more than 0.025, sulfur not more than 0.015.
③ Mechanical properties of Q345D seamless steel pipe: tensile strength 490~670MPa, yield strength: wall thickness less than or equal to 16mm not less than 345MPa, wall thickness 16mm~40mm not less than 335MPa, wall thickness greater than 40mm not less than 352MPa, elongation after fracture: longitudinal not less than 21, transverse not less than 19, low temperature punching -20℃: longitudinal not less than 40, transverse not less than 27
④ Heat treatment of Q345D seamless steel pipe: 880℃~940℃ normalizing
Q345D seamless steel pipe production process: cold drawing, hot rolling, hot expansion.
Q345D seamless steel pipe delivery status: hot rolling, heat treatment.
Q345D seamless steel pipe product outer diameter 21.3mm~762mm wall thickness 3mm~140mm

The usual length of the Q345D seamless steel pipe is 4000 mm~12000 mm. After negotiation between the supplier and the buyer, and with the above indication in the contract, steel pipes with a length greater than 12,000 mm can be delivered; steel pipes with a length less than 4,000 mm but not less than 3,000 mm can also be delivered, and the quantity should not exceed 5% of the total quantity of steel pipes delivered in this batch.

Steel pipes should be manufactured by hot rolling (extrusion, expansion) or cold drawing (rolling) seamless method. When the buyer specifies a method to manufacture steel pipes, it should be indicated in the contract.

Delivery status Steel pipes should be delivered in a heat-treated state. The heat treatment system of steel pipes should comply with regulations. The heat treatment system should be filled in the quality certificate.

Steel pipes directly rolled from ingots should be inspected at low magnification. No visible white spots, inclusions, subcutaneous bubbles, skin folding, and delamination are allowed on the acid immersion test piece of the steel pipe cross-section.

Cracks, folds, rolling folds, scars, and delamination are not allowed on the inner and outer surfaces of Q345D steel pipes. These defects should be completely removed, and the removal depth should not exceed the negative deviation of the nominal wall thickness. The actual wall thickness at the cleaned location should not be less than the minimum allowed by the wall thickness.

On the inner and outer surfaces of the steel pipe, the allowable depth of the straight line is as follows: cold-drawn (rolled) steel pipe: not more than 4% of the wall thickness, the maximum depth is 0.2 mm; hot rolled (extruded, expanded) steel pipe: not more than 5% of the wall thickness, the maximum depth is 0.4 mm. Other local defects that do not exceed the negative deviation of the wall thickness are allowed to exist.