SUS409 Stainless Steel Pipe
SUS409 Stainless Steel Pipe: Composition, Properties & Equivalents per JIS G4305
Comprehensive technical data on SUS409 ferritic stainless steel pipe according to JIS G4305, including chemical composition, mechanical properties, thermal and electrical characteristics, international equivalents, and application guidance for exhaust systems.
Cold forming, welding (TIG, MIG, resistance), bending, deep drawing, blanking, annealing at 780–850°C followed by rapid cooling
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SUS409 Stainless Steel Pipe Introduction
SUS409 is a cost-effective ferritic stainless steel designed primarily for automotive exhaust systems where oxidation resistance up to 700°C and good weldability are required. Containing 10.5–11.75% chromium with very low nickel, it provides adequate corrosion resistance in mildly aggressive environments while eliminating the cost volatility of nickel. The grade is typically supplied in the annealed condition and exhibits ferromagnetic behaviour. Its moderate strength, high thermal conductivity, and low thermal expansion make it suited for parts subjected to thermal cycling. Although the base specification JIS G4305 covers cold-rolled sheet and strip, the material is widely converted into welded pipes. For improved intergranular corrosion resistance after welding, the titanium-stabilised version SUS409L is often preferred.
SUS409 Stainless Steel Pipe Chemical Composition as per JIS G4305
The chemical limits for SUS409 ensure a stable ferritic microstructure with sufficient chromium for oxidation resistance. Carbon is kept low to maintain ductility and weldability. No intentional titanium stabilisation is specified in this grade, differentiating it from SUS409L.
| Element | Standard Value (max, unless range noted) | Remarks |
|---|---|---|
| Carbon (C) | 0.08 | Low carbon for weldability |
| Silicon (Si) | 1.00 | Deoxidizer; contributes to oxidation resistance |
| Manganese (Mn) | 1.00 | Austenite stabilizer, improves hot workability |
| Phosphorus (P) | 0.040 | Impurity; kept low to avoid embrittlement |
| Sulfur (S) | 0.030 | Impurity; low for improved cleanliness |
| Chromium (Cr) | 10.50–11.75 | Primary ferrite stabilizer for corrosion/oxidation resistance |
| Nickel (Ni) | 0.60 | Residual; low nickel provides cost stability |
| Other elements | — | Titanium or niobium not intentionally added; total other elements per standard |
SUS409 Stainless Steel Pipe Thermal and Electrical Physical Properties
Physical properties are approximate and can vary with production route and condition. Thermal expansion and conductivity data are provided for temperature ranges relevant to exhaust system design. SUS409 exhibits higher thermal conductivity and lower expansion than austenitic grades, reducing thermal stress.
| Property | Standard/Typical Value | Unit | Test Condition / Temperature Range |
|---|---|---|---|
| Density (ρ) | 7.75 to 7.80 | g/cm³ | 20°C |
| Young's Modulus (E) | 200 | GPa | 20°C |
| Shear Modulus (G) | 77 | GPa | 20°C |
| Poisson's Ratio (ν) | 0.28 | — | 20°C |
| Thermal Expansion Coefficient (α) | 10.8 | 10⁻⁶/K | 20–100°C |
| Thermal Expansion Coefficient (α) | 11.3 | 10⁻⁶/K | 20–200°C |
| Thermal Expansion Coefficient (α) | 11.9 | 10⁻⁶/K | 20–400°C |
| Thermal Conductivity (λ) | 25.0 | W/m·K | 100°C |
| Thermal Conductivity (λ) | 26.0 | W/m·K | 500°C |
| Specific Heat Capacity | 460 | J/kg·K | 20°C |
| Electrical Resistivity (ρₑ) | 0.60 | µΩ·m | 20°C |
SUS409 Stainless Steel Pipe Mechanical Properties
Mechanical requirements for SUS409 tubular products are normally taken from JIS G3459 for stainless steel pipes. The values below represent minimum tensile properties at room temperature for longitudinal test pieces. Elongation applies to pipe wall thickness up to 15 mm. The yield strength is defined as 0.2% offset.
| Property | Standard Requirement (min unless noted) | Unit | Test Condition |
|---|---|---|---|
| Tensile Strength (Rm) | 410 | MPa | Room temperature |
| Yield Strength, 0.2% (ReH) | 205 | MPa | Room temperature |
| Elongation (A) | 20 (longitudinal), 15 (transverse) | % | Gauge length 50 mm or 5.65√S0 |
| Hardness | ≤180 | HBW | Optional; typical for annealed condition |
SUS409 Stainless Steel Pipe Directly Equivalent Material Standards and Designations
| Country/Region | Standard | Grade/Designation | Remark |
|---|---|---|---|
| Japan | JIS G4305 / JIS G3459 | SUS409 | Base specification; non-stabilised ferritic grade |
| USA | ASTM A240 / A268 | 409 (UNS S40900) | Ti-stabilised required (Ti + Nb = 0.08+6×(C+N) min); chemically similar but stabilised |
| Europe | EN 10088-2 / EN 10217-7 | 1.4512 (X2CrTi12) | Ti-stabilised ferritic; Ni ≤ 0.50; direct substitute for welded applications |
| China | GB/T 3280 / GB/T 12770 | 0Cr11Ti / 06Cr11Ti (S11163) | Ti-stabilised; equivalent to welded pipe applications |
SUS409 Stainless Steel Pipe Application Introduction
SUS409 is engineered for moderate-duty corrosion and elevated-temperature service where cost efficiency is critical. Thanks to its ferritic structure, it resists stress-corrosion cracking and offers stable mechanical properties during thermal cycling. Typical uses include:
- Automotive exhaust system components (mufflers, pipes, flanges)
- Catalytic converter shells and heat shields
- Agricultural sprayer booms and exhausts
- Domestic heating appliance flue pipes
- General welded tubular structures and furnace parts
The grade can be formed and welded by common methods. For heavy-section welding or sustained high-temperature exposure, the stabilised variant SUS409L is recommended to prevent sensitisation.
Product Applications: Exhaust pipes and mufflers, Catalytic converter housings, Flexible couplings, Ducting for flue gases, Heat exchanger tubing (low-pressure side), Resistance welded mechanical tubing
Processed into products: Tail pipes and silencers, Engine exhaust manifolds (cold end), EGR (Exhaust Gas Recirculation) pipes, Fuel filler necks, Boiler baffles and flue liners, Automotive structural brackets (welded assemblies)
Application industries: Automotive, Agricultural machinery, Domestic heating and ventilation, Industrial furnace and heat treatment, General engineering
SUS409 Stainless Steel Pipe Similar / Alternative Material Recommendations
| Country/Region | Standard | Grade/Designation | Remark |
|---|---|---|---|
| Japan | JIS G4305 | SUS409L | Titanium-stabilised version with improved weld decay resistance |
| Japan | JIS G4305 | SUS410L | Lower Cr (11.5-13.5%), higher hardenability; slightly better strength |
| USA | ASTM A240 | 410S (UNS S41008) | Low carbon 12% Cr ferritic; comparable oxidation resistance, not stabilised |
| Europe | EN 10088-2 | 1.4003 (X2CrNi12) | Multipurpose 12% Cr utility stainless; welded condition, good corrosion performance |
| China | GB/T 3280 | 06Cr13 (S11306) | Low cost ferritic; similar corrosion level but slightly lower Cr |
Notes:
Welding considerations: SUS409 does not contain deliberate titanium stabilisation. Intergranular corrosion may occur in the heat-affected zone after welding if exposed to elevated temperatures (450–850°C) in corrosive service. For such applications, specify SUS409L or perform post-weld annealing.
Availability: Pipes are commonly supplied in the annealed and pickled condition per JIS G3459, with wall thicknesses from approx. 0.6 mm to 4.0 mm in standard diameters. Custom lengths and special surface finishes can be requested.
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