409 Stainless Steel Pipe

We offer a wide range of stainless steel pipes, categorized as follows:

By Manufacturing Process: Seamless pipes / Welded pipes

By Connection Type: Threaded pipes / Flanged pipes / Grooved pipes

By Application & Function: Exhaust pipes / Perforated pipes / Coated pipes / Customized pipes

409 Stainless Steel Pipe

409 stainless steel pipe is a ferritic stainless steel product that offers good oxidation and corrosion resistance, especially in high-temperature environments. It has lower chromium content than 304 or 316, which makes it more economical, while still providing adequate durability. With good weldability and thermal stability, 409 stainless steel pipe is widely used in automotive exhaust systems, heat exchangers, and other applications where moderate corrosion resistance and excellent heat resistance are required.

409 Stainless Steel Pipe – Chemical Composition (%)

409 Stainless Steel Pipe – Mechanical Properties

Hot Processing

Seamless Pipes: Hot piercing + multiple mandrel mill or rotary piercing steps.

Welded Pipes: Plate is rolled into a cylinder, welded, and then sized/straightened.

Features:

Seamless pipes are axially stretched from the billet, with strict control of wall thickness and diameter.

Heat processing of pipes requires extra attention to roundness and uniform wall thickness.

Welded pipes need careful control of weld seam position and stress in the heat-affected zone.

Stress Characteristics:

The circular cross-section generates hoop and axial stresses during heating and cooling, which must be relieved by annealing.

Heat Treatment

Annealing: After hot rolling or welding, 409 stainless steel pipes are annealed at approximately 800–900°C to relieve internal stresses, improve ductility, and enhance corrosion resistance.  The pipe is then cooled under controlled conditions to stabilize dimensions and shape.

Stress Relief Annealing: For formed or welded pipes, a short low-temperature anneal below 400–450°C is often applied to remove residual stresses caused by welding or bending.

Notes:

Annealing is essential for 409 ferritic stainless steel due to its lower ductility and corrosion resistance.

Processes such as solution treatment, precipitation hardening, or high-temperature tempering are not applicable to 409 stainless steel pipes.

Features of 409 Stainless Steel Pipe

Ferritic Structure: 409 stainless steel has a ferritic crystal structure, providing moderate strength and good resistance to oxidation at high temperatures.

Corrosion Resistance: Suitable for mildly corrosive environments, such as automotive exhaust systems;  less resistant than austenitic grades like 304 or 316.

Heat and Oxidation Resistance: Maintains shape and strength at elevated temperatures, making it ideal for exhaust and high-temperature applications.

Formability: Good for rolling, bending, and welding, though ductility is lower than austenitic stainless steels.

Cost-Effective: Provides a balance of mechanical properties, heat resistance, and corrosion resistance at a lower cost compared with higher-grade stainless steels.