Q355B LSAW Steel Pipe DN800

Q355B LSAW steel pipe DN800: the main pipe for large-scale key projects.

Q355B LSAW steel pipe DN800 (nominal diameter is 800mm, corresponding external diameter is about 813mm) is a large pipe made of Q355B low alloy material and longitudinal submerged arc welding technology, which conforms to GB/T 9711 and GB/T 1591-2018 standards, has super-large flow transportation, super-high structural stability and reasonable economy, and is widely used in large-scale key transportation projects such as municipal, industrial and energy. Its core value lies in the large-scale flow advantage of DN800 specification and the efficient adaptation of Q355B material, which has become the benchmark choice for super-large centralized transportation scenes. This paper analyzes its core characteristics and application value with the subtitle of question sentence.

1. Material adaptation: Can Q355B bear DN800 working condition?

Q355B low-alloy high-strength carbon steel can stably bear DN800 working condition, and its yield strength is ≥355MPa, tensile strength is 470-630MPa, which is more than 50% higher than that of Q235. It can withstand the pressure of 16-18MPa, and calmly cope with internal pressure, soil load, environmental impact and medium erosion in large-diameter transportation. The impact energy of this material at -20℃ is ≥34J, and its low-temperature toughness is excellent. It is suitable for underground laying in cold areas, and it is easy to weld and resist corrosion. The alloy elements such as vanadium and titanium can enhance the corrosion resistance, accurately match the LSAW process, control the cost while ensuring the strength, and the cost performance ratio far exceeds that of high-alloy large pipes.

2. Specification and process: How to balance super-large flow and structural stability?

Compared with DN750, DN800 specification improves the transportation efficiency by more than 8%, which can meet the needs of centralized energy supply and industrial mass media transportation in super-large urban areas and adapt to large-scale centralized transportation scenarios. Using LSAW longitudinal submerged arc welding +UOE precision forming process, the weld strength is equal to that of the base metal, the stress distribution is uniform, and there is no hidden danger of stress concentration in spiral welded pipe; After forming, the residual stress is eliminated by expanding and tempering, and the tolerance of outer diameter is controlled within 0.5%, which adapts to various wall thickness specifications and ensures the long-term structural stability of buried and open-air laying.