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X-DM!!
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Discussion Starter #1
Does anyone know the differance between 304 and 409 in stainless steel grades?
Thanks in advance,
Rod.
 

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known as tibbo
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2,033 Posts
gee its been a few years but from memory
*304 std stainless steel
*316 marine grade s/s
409 and 403 is magnetic s/s
* are easier to weld, beld and anneal for bending and are not magnetic
409/430 weakens when you weld it because is has less carbon but i think it has a 'chrome' finish and does not come in 'satin'
may is ask what application you want to know?

If only i didnt throw out my old tafe workbooks i could tell you exactly
 

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X-DM!!
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Discussion Starter #3
Thanks tibbo, I have seen differant exhaust systems with these 2 differant gradings and wondered what they were. Doesn't say much for my 2 year welding course I did in the late 70s. I should say doen't say much for my memory.
 

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409 was apparently developed for exhaust systems as a cheaper alternative to 304. It normally only comes in a satin finish.

304 is your cheapest of the quality stainless steels (316, 321). These have a lot more corrosion resistance. If you look for Algenhy Lunghy in the USA or something like that they will have material data sheets, they invented 409 I believe.
 

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If Only I Had Lexus Power
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827 Posts
In terms of Exhaust

Commercial Grade (Rusts extremley quickly)
ACMS (Aluminium Coated Mild Steel) (Most manufacturers use this mostly)
304= Good,
409= Not so good but still alot better than ACMS

Most people use 409 if they are buildeng an stainless exhaust (still does the job well)

Here are some prices on a 3mt length of 3in straight exhaust tube for you to compare against

ACMS:$100
Commercial Grade:$75
409:$190
304:$335

You can quite clearly see the diffrences, and bending it depends on your dies and wall thickness finish etc although you wouldent want to bend 3in on a press bender
 

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X-DM!!
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1,114 Posts
Discussion Starter #6
Thanks guys, you have been very helpful and thanks for that price break down redGhia
now I can see why some systems are more expensive then others.
Cheers,
Rod.
 
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When you look at Jap stainless steel turbo exhaust manifolds their TIG weld joins have a golden colour to them.Does anyone know whether they use a special filler rod (say to prevent cracking) or could it be the grade of stainless they use that gives the joins this golden colour. My stainless tig welds never have this colour.
 

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known as tibbo
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The higher quality filler wire will produce nice gold and blue welds.. We used to use 316 grade as our wire and you could get some pearler welds happening.. Almost was a shame to grind them off
 
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I use argon. Will try and use a higher quality filler wire.
Any idea where to get mandrel stainless bends for manifold manufacture direct from the bender. The place I get them from are a rip off but I cant find out who supplies them.
 

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pR()rN_*
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No australian Manufactures use ACMS at all anymore.
Ford, Holden, Toyota, Mitsi all use 304 grade stainless.
 

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If Only I Had Lexus Power
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yes but its still used in the aftermarket
 
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