724L Seamless Tube Technical Manual

Material properties and manufacturing process 

724 seamless pipe is made of 724LN stainless steel (UNS S31726), which is a low-carbon, high-molybdenum austenitic stainless steel. The composition uniformity is ensured by vacuum melting process. Its core properties include: 

(1) Corrosion resistance: It performs well in strong corrosive media such as urea melt and ammonia water, which is better than ordinary 316L stainless steel; 

(2) Low temperature toughness: It still maintains good ductility at -196℃ and is suitable for deep cold working conditions; 

(3) Welding performance: TIG/MIG process is required, and the joint oxide needs to be thoroughly cleaned before welding. 

Performance advantages 

(1) High pressure tolerance: The seamless structure has no weld defects and the pressure bearing capacity is above 1.2MPa, which is suitable for high temperature and high pressure environment; 

(2) Surface treatment compatibility: The corrosion resistance can be improved by pickling and passivation, or hot-dip galvanizing can enhance the adaptability to high humidity environment in agriculture; 

(3) Dimensional accuracy: The inner wall smoothness Ra≤0.8μm, which reduces the fluid conveying resistance.

 Typical application areas

1. Chemical equipment

(1) Urea synthesis tower, reactor lining pipe, resistant to 190℃ high-pressure corrosive media;

(2) Ammonia pipeline, resistant to liquid ammonia stress corrosion cracking.

2. Energy and infrastructure

(1) Polyurethane insulation pipe working layer, used for heating/cooling fluid transportation at -50℃~120℃;

(2) Large diameter fluid pipe (DN≥300mm), for transportation of oil, natural gas, etc.

3. Special environment

(1) Agricultural greenhouse heating pipe, resistant to humidity above 90% after galvanizing；

(2) Heavy machinery workshop heat dissipation pipe, resistant to vibration and zero leakage for five years.