Raw materials for carbon steel pipe fittings (such as elbows, tees, flanges, reducers, etc.) are mainly selected according to the manufacturing process and application pressure rating of the fittings. Specific classifications are as follows:
1. Steel Plate & Strip
This is the most commonly used raw material for manufacturing large-diameter pipe fittings.
- Carbon structural steel plates: such as the Q235 series (formerly known as Grade A3 steel), often used for large-diameter elbows, tees or flanges in low-pressure piping systems. These materials feature moderate strength, low cost and good weldability.
- High-quality carbon structural steel plates: such as 20# steel plate, commonly used for medium and low-pressure pipe fittings, with better mechanical properties and toughness than ordinary carbon steel.
- Steel plates for pressure vessels: such as Q345R (formerly 16MnR), a low-alloy high-strength steel, often used for fittings subject to relatively high pressure or temperature, widely applied in petrochemical equipment.
2. Seamless Steel Pipe
This is the main raw material for manufacturing medium-high pressure and small-diameter pipe fittings. Fitting factories usually purchase cut-to-length seamless steel pipes and process them into elbows, tees and other products by processes such as push forming, hot pressing or cold drawing.
- High-quality carbon structural steel seamless pipes: the most typical grade is 20# steel (corresponding to international standards such as ASTM A106 Gr.B). It is the most general-purpose fitting material, suitable for conveying water, steam, air, oil and other common media.
- High-pressure seamless pipes for boilers: such as 20G, with higher high-temperature strength and oxidation resistance, specially used for pipe fittings in high-temperature and high-pressure boiler piping systems.
3. Forged Round Bar
Mainly used for manufacturing flanges and high-pressure thick-walled pipe fittings.
- Carbon structural steel forgings: such as Q235 or 20# forgings, for general-purpose flanges.
- Alloy structural steel forgings: such as 16Mn (Q345) or 45# steel, for high-pressure flanges and fittings requiring higher strength or wear resistance.
4. Cast Steel
Mainly used for manufacturing pipe fittings with complex shapes that are difficult to produce by welding or forging, or special fittings with extremely high pressure resistance requirements.
- Carbon cast steel: such as WCB (the most commonly used carbon steel casting grade, corresponding to standard ASTM A216). WCB fittings feature good strength and impact resistance, widely used in the manufacture of valves and fittings in the petroleum, chemical and power industries.
Summary
In practical applications, 20# steel (seamless pipe or plate) is the most common general-purpose raw material; Q235 is mostly used for low-pressure large-diameter welded fittings; Q345R is used for medium-high pressure vessel fittings; and WCB is the preferred material for cast steel fittings.
