409 stainless steel is a Ferritic steel that offers good mechanical properties and high-temperature corrosion resistance. It is commonly considered as a chromium stainless steel, with applications in exhaust systems of automobiles and applications that demand weldability.

Applications

Automotive and truck exhaust systems (including manifolds and mufflers)

Agricultural machinery (spreaders)

Heat Exchangers

Fuel filters

Comparison

Grade	UNS No	Old British		Euronorm		Swedish SS	Japanese JIS
		BS	En	No	Name
409	S40900	409S19	–	1.4512	X6CrTi12	–	SUH 409

Composition

Grade		C	Mn	Si	P	S	Cr	Ni	Ti
409	min. max.	– 0.08	– 1.00	– 1.00	– 0.045	– 0.045	10.5 11.75	– 0.5	6x C 0.75

Mechanical Properties

Grade	Tensile Strength (MPa) min	Yield Strength 0.2% Proof (MPa) min	Elongation (% in 50mm) min	Hardness
				Rockwell B (HR B) max	Brinell (HB) max
409	450	240	25	75	131

Sizes

Hot Rolled Process – OD 30-500mm ; WT 3-60mm ; L 6-12meter

Cold Drawn Process – OD 10-200mm ; WT 0.5-20mm ; L 1-12meter

Cold Rolled Process – OD 6-200mm ; WT 0.1-20mm ; L 1-12meter

Surface

Acid pickling – pre-passivation process of treating stainless steel parts with an acid solution, typically hydrochloric or sulfuric acid, which can remove oxide scale and heat tint while dissolving steel flecks embedded in the part.

Polishing – P grade sandpaper: P150, P200, P250, P300, P400, P500, P600, P700, P800

Inspection

Chamical analysis / Tensile test at room temperature / flattening test / ring tensile test / drift expemdomg test / ring expanding test / leak tightness test / Tensile test at elevated temperature / impact test at room temperature / impact test at low temperature / eddy current test / ultrasonic test / magnetic flux leakage test

Corrosion Resistance

409 stainless steels have excellent resistance to exhaust gas and atmospheric corrosion, superior to that of 410 martensitic grades with 12% chromium and 3CR12. However, the corrosion resistance is lower than that of grade 430 steels containing 17% chromium. The surface of grade 409 steels is liable to mild corrosion, which limits the usage of steels for decorative purposes.

Heat Resistance

409 stainless steels offer scaling resistance at temperatures up to 675°C during continuous operation, and up to 815°C under intermittent conditions. These temperatures pertain to specific service environments.

Welding

Grade 409 steels must be pre-heated to temperatures of 150 to 260°C before welding. Although grade 430 and 409 filler rods or electrodes can be used during welding of grade 409 steels, grade 309 electrodes or filler rods are strongly recommended by AS 1554.6. Care should be taken to weld grade 409 steels with minimum heat, in order to mitigate grain growth.