430 Stainless for exhaust application?

[Wicsteve]

We'd like to substitute 430 Stainless for 409 stainless for use in a muffler / motorcycle exhaust application. Our factory touts that it has better corrosion resistance than 409 and is, in their case, easily obtained. There is some concern that 430 stainless could become brittle in this particular application.

From the AZoM web site regarding 430 Stainless Steel:
"...resists oxidation in intermittent service up to 870°C and to 815°C in continuous service. This grade may become brittle at room temperature after prolonged heating in the 400-600°C range. ... Slow cooling from 540-400°C will cause embrittlement".

It is unclear however as to what "slow cooling" means when applied to sheetmetal or even if these statements are applicable to us. For a muffler application, we'd certainly would be operating within the 400 - 600C range but sheetmetal parts should cool rather quickly. Should there be a concern?

 

[metengr]

I would remain with the 409. The 430 stainless steel is less desirable from a weldability standpoint. You can review for yourself

http://www.alleghenyludlum.com/ludlum/Documents/AL430.pdf

 

[TVP]

I agree, Type 430 is less desirable for this application than Type 409. The carbon content is too high...

 

[swall]

What is the reason for your inquiry? Are you looking for something that lasts longer or is simply more cosmetically appealing?

 

[Wicsteve]

Durability, cost, and availability are the driving factors for material selection. In the past, we've used 430 stainless for several very small mufflers without failures but this time the life of the exhaust system needs to be much longer and the vibration that it is exposed to is more severe. We really don't need surface rust while the unit is still in the showroom but if the muffler shells crack or the baffles come loose due to cracks or failed welds then we'd have a disaster.

 

[EdStainless]

If your 430 is low carbon (<0.05%) then go for it.

even 409 will embrittle over time so I don't see that as a big difference

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[Wicsteve]

Thanks, everyone.

 

[dgallup]

I thought 439 was the preferred material for exhausts. Improved corrosion resistance & formability.

http://www.aksteel.com/pdf/markets_products/stainless/ferritic/439_Data_Bulletin.pdf

 

[CoryPad]

409 is preferred for cost, 439 is used when more corrosion resistance is needed.

 

[unclesyd]

i don't believe that 430 SS will not stay pretty in this application based on my personal experience with using it at our plant. It quickly forms a heavy reddish brown oxide scale on heating and exposure to the elements. Our original HNO3 plants were about 75% 430 piping.

We made some very precision parts from 430, 18+ Cr. and we have purposely form a tight oxide surface after machining. If we didn't force this oxide the part would become useless after 2 or 3 cycle in our process.

 

[EdStainless]

The only time that 439 has an advantage over 430 is when you are welding.
The 430 spec has two grades, low C and high C. The low C is ferritic and behaves much like 439.

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