Different uses of stainless steel fittings, carbon steel fittings, and alloy steel fittings
1: Carbon steel fittings (20 #, Q235, ASTM A234 WPB etc)
Material characteristics
The most cost-effective, moderate strength, easy to weld and process, not resistant to corrosion, high temperature, easy to rust, preferred for normal temperature and pressure use.
main purpose
Water supply and drainage, municipal engineering: water supply pipelines, ordinary sewage pipelines, heating and water supply main pipelines, low-pressure gas transmission.
General industrial fluids: compressed air at room temperature, cooling water, ordinary oil products, and transportation of non corrosive media.
Supporting steel structures for buildings, low-pressure pipelines for fire sprinklers, and circulating water for factory buildings.
Medium and low pressure thermal pipeline network (temperature ≤ 350 ℃), power plant auxiliary cooling water pipeline.
Limitations: Cannot be used under acidic, alkaline, seawater, and high temperature conditions.
2:Stainless steel fittings (304, 316L, 321)
Material characteristics
Acid and alkali corrosion resistance, rust prevention, high cleanliness, better high-temperature resistance than carbon steel, and relatively high cost.
main purpose
Food and pharmaceutical industry: beverages, brewing, pharmaceutical purified water, dairy transportation (mostly sanitary grade pipe fittings).
Chemical corrosion conditions: weak acid and weak alkali, salt solution, seawater, sewage desulfurization pipeline; 316L is resistant to chloride ions and is commonly used in seawater and chemical waste liquids.
Pure water, high-purity gas: Electronic factory ultrapure water, nitrogen/oxygen clean pipelines.
Kitchen and bathroom, municipal drinking water, hot spring water, boiler high-temperature soft water pipeline.
Petrochemical light oil products and fine chemical material pipelines.
304: Conventional weak acid, drinking water; 316L: seawater, chloride ion environment, strong corrosive medium.
3:Alloy steel pipe fittings (16Mn, 12Cr1MoV, P91/P92, 15CrMo and other chromium molybdenum alloys)
Material characteristics
High temperature resistance, high pressure resistance, creep resistance, excellent high-temperature strength, partially heat-resistant and hydrogen resistant, with the highest cost.
Main purpose (exclusive for high temperature and high pressure)
Thermal power/thermoelectric boiler: boiler water-cooled wall, superheater, main steam pipeline (high temperature and high pressure above 500 ℃, commonly used 12Cr1MoV, P91).
Petrochemical refining unit: hydrogenation unit, cracking furnace, high-temperature heavy oil pipeline, inlet and outlet of hydrogenation reactor (in high temperature and high pressure environment near hydrogen).
Coal chemical and fertilizer plants: synthetic ammonia high-pressure pipelines, high-temperature process gas pipelines.
High pressure hydraulic, high-pressure gas: high-pressure hydrogen, high-pressure steam, high-pressure boiler main pipeline.
16Mn (Q345): Low temperature medium and high pressure vessels, low-temperature process pipelines; Chromium molybdenum steel: High temperature and high pressure petrochemical, power plant core pipelines.
