Description

SS 409 plate steel is a 12% chromium, titanium stabilised ferritic stainless steel. It has fair resistance to corrosion and oxidation at high temperatures. In the annealed condition SS 409 plate steel is ductile, does not work harden and can be formed using a variety of roll forming, bending or mild pressing/ stamping operations.

SS 409 plate steel is a low carbon, dual stabilized (titanium and niobium) ferritic stainless steel containing 18% chromium. SS 409 plate steel has good corrosion resistance in moderately corrosive environments and good oxidization and creep resistance at elevated temperatures.

Machining this alloy produces tough, draggy chips with heavy build-up. While this alloy can be machined in the annealed condition, it tends to perform better in the cold drawn or heat treated condition.

ASTM A240 Stainless Steel 409 Chemical Composition

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

Typical applications

Both 409 and 1.4509 have good corrosion resistance at higher temperatures than standard ferritics and are best utilised in mildly corrosive environments where resistance to scaling at moderate temperatures is required. These grades were first developed for the automotive industry but have since been used in other applications:

• Exhaust systems and Catalytic converters.

• Electrical distribution boxes, covers and turnstiles.

• Solar water systems and geysers.

Mechanical properties In accordance with ASTM A240 and EN 10088-2 Maximum recommended service temperature

General corrosion resistance 409 is significantly more corrosion resistant than mild or low alloy corrosion resistant steels. It has lower corrosion resistance than the higher chrome standard ferritics. It is best suited in mildly corrosive conditions where aesthetics are not a prime requirement. A light surface patina or discolouration may form and this will, to some extent, retard further corrosion.

Thermal processing and fabrication Annealing Annealing (softening) is achieved by heating to the following temperatures at a rate of 3.5minutes/mm followed by air quenching.

409: 820-920⁰C 1.4509: 920-1,020⁰C

Stress Relieving

Stress relief after welding is not usually required. Should this be necessary, temperatures between 200ºC and 300ºC are recommended for 60 minutes per 2.5mm.

Hot-working

Initial forging and pressing temperature range: 950ºC to 1050ºC Finishing temperature below 750ºC. Avoid extended holding times above 1000ºC as excessive grain growth takes place which reduces ductility.

Note: All hot working operations should be followed by annealing and then pickling and passivation to restore the mechanical properties and corrosion resistance.

Cold working

409 and 1.4509 have fair formability characteristics with useful mechanical properties. Their ductility allows them to be formed by bending and deep drawing. They do not undergo significant work hardening when cold formed.

Welding

409 and 1.4509 are prone to grain growth in the heat-affffected zone. As such, the tensile, fatigue and toughness properties in the welded condition are relatively poor. They should thus not be used for applications where tensile or dynamic loading will be experienced.

stainless steel plate 63013