Performance, chemical composition, and manufacturing details of Q345D seamless steel pipe

Implementation standards of Q345D seamless steel pipe: GB/T8162 seamless steel pipe for structure, GB/T8163 seamless steel pipe for conveying fluid, GB/T6479 seamless steel pipe for high-pressure and high-temperature fertilizer equipment. Except for GB/T8162 seamless steel pipe for structure, GB/T8163 and GB/T6479 should meet the requirements of the pressure pipeline type test rules.

Chemical composition of Q345D seamless steel pipe: 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.

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

Q345D seamless steel pipe heat treatment system: 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 Q345D seamless steel pipe is 4000mm~12000mm. After negotiation between the supply and demand parties and indicated in the contract, steel pipes with a length greater than 12000mm can be delivered; steel pipes with a length less than 4000mm but not less than 3000mm can also be delivered, and the quantity should not exceed 5% of the total quantity of steel pipes delivered in this batch.

Q345D seamless steel pipes should be manufactured by hot rolling (extrusion, expansion) or cold drawing (rolling) seamless method. When the demander specifies a method to manufacture steel pipes, it should be indicated in the contract.

Delivery status of Q345D seamless steel pipes 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 included in the quality certificate. Steel pipes directly rolled from ingots should be inspected at low magnification. No visually 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, scarring, and delamination are not allowed on the inner and outer surfaces of Q345D seamless 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 Q345D seamless steel pipes, the allowed depth of the straight line is as follows: cold drawn (rolled) steel pipes: not more than 4% of the wall thickness, the maximum depth is 0.2mm; hot rolled (extruded, expanded) steel pipes: not more than 5% of the wall thickness, the maximum depth is 0.4mm. Other local defects that do not exceed the negative deviation of the wall thickness are allowed to exist.