best type of stainless

[deano1]

Hi guys,
Hope you boys can help i`m adding a few bits to the exaust system on my bike, i`m tiging round pipe 1.5mm thick and 35 and 50mm o\d respectivley i`m about to order some tube but i`m a bit puzzled with the different grades ie- 304 and 316 etc can you guys tell me what would be the correct grade of stainless to order for this project, thanks all.

 

[Ashg]

304 is best for an exhaust

 

[Hitch]

304 would be the easiest route imo.
There are other grades that are used for exhausts, but will be harder to get hold of.

 

[dannyweld]

304 is best for an exhaust

would 304 be better than 316, how come?

 

[RichardG]

I understand its less likely to fracture.

 

[dannyweld]

I understand its less likely to fracture.

interesting.

 

[Normsthename]

316 is much more expensive than 304, and is a Medical / Food grade.
316 does weld slightly better than 304, but there is not a lot in it.
I built a Garden Feature over a year ago for my brother out of 304 Stainless Steel.
It has been outside since in all weathers, as well as having water constantly cascading down it.
It has welded seams and the metal and welds are all still bright and clean

Andy

 

[Welderpaul]

I have always used 316 for external and 304 for internal. Often been tempted to use 304 for external due to cost and know other fabbers who regularly do it, but i don't know if i want to take the risk?

 

[Paul.]

Main thing Paul is to assess what the jobs going to be exposed to, if your jobs on the sea font for example, or a similar corrosive atmosphere 316 would be the obvious choice, much of my work is in the food industry particularly meat processing and 304 is used without problems in most areas, although some chemical cleaners will eat almost anything, one of my customers has just had a major fire, and the smoke from burning insulation has eaten through the stainless framework of some of the machinery, brand new factory as well, 3 months worth of my work written off, shame really Ill have to do it all again

 

[Welderpaul]

The bulk of external stainless is in city centre locations, not a particularly aggressive exposure. 316 seems to be in most architects specifications for external work.

 

[Paul.]

They spec 316 to cover themselves, which is fair enough i suppose, about 7 years ago I made some handrailing for a local casino / cinema complex It was made from 304 tube cos thats all we could get in the timescale we had to do the job, Its outside on one of the busiest road junctions in town, exposed to traffic fumes, road salt etc, and still as bright as the day I fitted it.

 

[TechnicAl]

In general 316L has better corrosion resistance than 304L but in the atmosphere created by an exhaust, ie hot and sulphurous, it probably wont make much difference which one you use.
They usually use 410 stainless for exhausts because its strong, has better reistance to sulhurous atmospheres. The Sulphur attacks the Nickel in the 304L and 316L but the 410 is a low carbon 12% Chromium steel with little or no Nickel.

 

[Shox Dr]

Whatever you decide to use make sure you use the correct type of rod, if not you will get a colour difference where the weld is. Don't forget to back purge as well

 

[dannyweld]

i always use 316 wire on what ever grade, mig and tig, its a bit cheaper than 304 wire for some reason. 316 is marine grade, its got some moly in it and does'nt pit but is hard as hell. 304 is the standard really and has the widest range, its the material of choice as far as i'm concerned. if you want seamless, which you may need for certain pipe situations, you may need to go up to 316.

 

[zardoz]

is 316 what they call surgical steel ?

 

[Paul.]

Surgical steels are usually martensitic, Its generally harder than 304 and 316, which are austinetic, typical martensitic grades are 410, 416, 420, 431,

A general rule is if the grade starts with a 3, its Austinetic, and 4 will be ferritic or martensitic

 

[dannyweld]

to be honest 400 is'nt a true stainless, its the stuff they use for cladding your american type diner with. its magnetic to. interestingly, i got my self a super duper powerful little magnet and it sticks to the hot rolled 304 but does'nt to the cold reduced 304. have seen some surgical probes been made on cnc lathe, they were out of 316. surgical stuff that has to be super hard is non stainless. if its going near seawater than it better be 316.

 

[Shox Dr]

Dannyweld.
We only use 316L rod at work, so I used that to repair a rear mudguard off a T140 Triumph, welded up fine, just as I expected, however when I polished it up you could see a difference in colour. A mate also had a set of pipes made for his Harley, said they would be mandrel bent from a single piece of tube, but 2 yrs down the line and you can clearly see where they joined the bends as the weld is showing a different colour

 

[dannyweld]

Dannyweld.
We only use 316L rod at work, so I used that to repair a rear mudguard off a T140 Triumph, welded up fine, just as I expected, however when I polished it up you could see a difference in colour. A mate also had a set of pipes made for his Harley, said they would be mandrel bent from a single piece of tube, but 2 yrs down the line and you can clearly see where they joined the bends as the weld is showing a different colour

hi, i can see your point there, with what i do a bit of pickle, powerwash and a wipe of tinners and job done, so its horses for courses as they say. i even use the 316 wire when tig welding bright mild if i'm stuck. i find the 316 mig wire better as its a bit stiffer and less likley to snag or bend than the 304

 

[TechnicAl]

to be honest 400 is'nt a true stainless, its the stuff they use for cladding your american type diner with. its magnetic to. interestingly, i got my self a super duper powerful little magnet and it sticks to the hot rolled 304 but does'nt to the cold reduced 304. have seen some surgical probes been made on cnc lathe, they were out of 316. surgical stuff that has to be super hard is non stainless. if its going near seawater than it better be 316.

Providing the Chromium content is 12%+ its stainless. 410 is 12% Cr. This is the ORIGINAL stainless developed by Harry Brearley in Sheffield.

It should be the cheapest but its not as poplular as 304L / 316L and this keeps the price higher, its also more difficult to work.

The best stainless for a knife blade is 440 grade.