What issues should be noted when manufacturing petrochemical equipment using 310S stainless steel

What issues should be noted when manufacturing petrochemical equipment using 310S stainless steel pipes? 

1. Performance risks under high-temperature conditions

1. Thermal expansion control: The thermal expansion coefficient is high at high temperatures (14.5×10⁻⁶/℃). The equipment design must incorporate compensation structures (such as expansion joints) to prevent weld cracking due to thermal stress. 

2. Prevention of Creep Damage: When operating continuously at temperatures ranging from 800 to 1200 degrees Celsius, it is necessary to ensure that the working stress is below the creep strength threshold (for example, the allowable stress should be ≤ 20 MPa at 1000 degrees Celsius), and regular inspections for intergranular corrosion tendencies should be conducted. 

II. Difficulties in Welding and Processing Techniques

1. Control of Welding Defects:

(1) High nickel content can lead to hot cracks in the weld seam. Therefore, a small current and rapid welding process should be adopted. The welding rod to be used is E310-16 (A402). Preheating at 150℃ before welding and slow cooling after welding are required.

(2) To prevent the formation of carbides in the welding area, a solution treatment (water cooling at 1050~1100℃) should be carried out after welding to restore the corrosion resistance. 

2. Cold work hardening: Austenite structure is prone to hardening during cold forming. The deformation amount should be controlled within ≤ 20%. If necessary, post-processing annealing (holding at 300 - 350℃ for 2 hours) should be performed to relieve stress. 

III. Protection in Corrosive Environments

1. Sulfide Corrosion: In media containing H₂S, the concentration of Cl⁻ should be controlled to be less than 50 ppm to prevent intergranular corrosion. Surface chromium plating (thickness ≥ 5 μm) or coating with fluororubber can be used to enhance protection. 

2. High-temperature oxidation protection: When exposed to an oxygen-rich and high-temperature environment for a long time, a Cr₂O₃ oxide layer may form on the surface. However, it is necessary to regularly check for the peeling of the oxide layer to prevent pipeline blockage. 

IV. Cleaning and Installation Requirements

1. Surface Contamination Control: During the processing, avoid iron ion contamination (such as by contacting carbon steel tools). After welding, the surface should be treated with a nitric acid + hydrofluoric acid solution (volume ratio 5:1) for passivation to remove surface impurities. 

2. Stress concentration avoidance: The bending radius of the pipeline should be ≥ 3 times the pipe diameter to prevent fluid erosion and wear caused by right-angle elbows. When using flange connections, the bolt torque should be uniform to avoid excessive stress in a localized area. 

V. Key Points for Inspection and Maintenance

1. Non-destructive Testing: 100% radiographic testing (RT) and penetrant testing (PT) must be conducted on the welded joints, with a focus on detecting micro-cracks. Regularly, the wall thickness of the pipe should be monitored using an ultrasonic thickness gauge (allowing a corrosion rate of ≤ 0.1mm/year). 

2. Condition Monitoring: Continuously monitor the operating temperature and pressure to prevent the occurrence of overheating (above 1200℃), which could lead to coarse grain formation and deterioration of mechanical properties.