304 Stainless Steel Flange

304 flange material verification

1. Material verification

Test items True 304 (ASTM A182) Fake 201/202 Risk

Cr content ≥18.0% 14.0-16.0% Passivation film failure

Mn content ≤2.0% ≥7.0% Impact resistance decreased by 60%

Ni content ≥8.0% ≤4.5% Intergranular corrosion accelerated by 5 times

2. Our product quality control

Triple verification:

① Spectrometer detection of incoming raw materials to ensure accuracy ±0.1%

② 10% sampling PMI point measurement of each batch of finished products

③ MTR report matches smelting furnace number

Performance comparison of all 304 stainless steel flanges

Type Maximum pressure Seal leakage rate Applicable media case

Loose sleeve flange Class 900 ≤0.005% Acid and alkali storage tank (pH 5-9)

Blind plate Class 2500 0% (static seal) Storage tank maintenance isolation

Butt welding neck Class 2500 ≤0.001% Steam pipe (200°C)

Threaded flange Class 300 ≤0.02% Instrument air (DN≤50)

Corrosion failure threshold

1. Environmental corrosion threshold

Medium Safe use range Failure case

Temperature ≤150°C Superheated steam (204°C intergranular corrosion)

Chloride ion (Cl⁻) ≤50ppm Coastal power plant cooling pipe (3 years pitting)

pH value ≥4.5 Yogurt production line (pH=3.8 corrosion)

2. Protection plan

pH 3.0-4.5: Upgrade 316L flange (molybdenum acid corrosion resistance)

>150°C: Choose 321 flange (titanium stabilization)

Cl⁻ 50-200ppm: Pickling passivation + nitric acid passivation maintenance every six months

Avoidance guide (FAQ)

Q1: Why is the price difference of the same batch of 304 stainless steel flanges 30%?

Answer: Beware of three traps:

① Non-standard thickness: Thin flange neck (ASME minimum thickness + 20%)

② Fake 304: Use 201 to fill 304 (nickel <5%)

③ Unpassivated: Surface free iron causes rust

Q2: Does the blind flange need a gasket?

Answer: Must! Recommended:

Class ≥ 900: Metal toothed gasket (sealing pressure ratio > 200MPa)

Class ≤ 600: Graphite composite gasket (compression rate 18%)

Q3: Can threaded flanges be used for high-pressure gas?

Answer: Prohibited! There is a risk of leakage in the threaded structure:

Combustible gas: Class 150 only

Nitrogen/air: Up to Class 300@38°C

Choosing us means choosing peace of mind:

Failure insurance: Provide 10-year material authenticity guarantee, if it is a fake 304 stainless steel flange, the compensation will be 10 times)

Anti-corrosion innovation: Exclusive electrolytic polishing process (Ra≤0.8μm), corrosion resistance increased by 50%

Inventory cloud map: Real-time display of DN15-DN800 inventory geographical distribution (support nearby transfer)