stainless steel??

[johnakay]

would you say that 3mm s/steel would be just as strong as a 4mm to 5mm mild steel plate?
I was thinking of getting some bracket made rather than me welding two pieces together as in picture below. its for a cbr500 motorbike back rest and racks etc .
it only has a small mounting point .
the bracket is welded to 19mm tubing.

 

[Rig Pig]

Stainless is strong and won't corrode however it has a nasty habit of eating carbon steel that it is attached to in a damp environment!

 

[TechnicAl]

It depends on the condition. Annealed stainless will be weaker than cold worked mild steel

 

[johnakay]

the s/steel will be laser cut.
and it will be welded ,so will this be called Annealed stainless??
the bracket will be supporting the rack or both back rest etc as in the picture.
as you can see ..on a bike it will have a up and down motion as with all racks etc.
this will no doubt put a stress on the 2 brackets.
I put a sticker on the rack max load 5kgs(about 11 lbs)
also it will be powder coated.
what I have been doing as you can see in the picture.
I put a small bend in the middle to give it more strength than if I'd left it flat.
welded it on both side to the horizontal plate with slots in, with a backrest I weld another narrow plate underneath the top bracket.
the bracket plate is 3mm thick.
what I want is to make it look more professional and robust.

 

[hotrodder]

the s/steel will be laser cut.
and it will be welded ,so will this be called Annealed stainless??

Almost certainly not but it depends on what the profile cutters typically use/keep in stock... the place i use, unless you specifically ask for something else you'd get 2B finish. http://www.aalco.co.uk/datasheets/Stainless-Steel-Surface-Finishes_135.ashx explain what 2B and a bunch of the other finishes are

There's next to nothing between the two materials with regards to Young's modulus i.e. regardless of yield strength a slightly thinner stainless bracket will have more 'elastic give' if/when someone manhandles the bike using the rack and so 'feel' less strong. This side of things could be fixed by adding an extra fold to the bracket along the lines of the red line i added to the pic



If i'm picturing things right then you'd have a couple of folds to make to the bracket and when you weld it to the tube a small weld to the red fold which'd stiffen things up

 

[johnakay]

what you see in the picture is a 3mm plate.
no way could I give a small enough fold on that.
I don't really want to start doing more work on a laser cut plate thats the whole idea of getting laser cut,
so I can just weld it on .

 

[hotrodder]

If you're currently using 3mm mild steel then what's the relevance of this

would you say that 3mm s/steel would be just as strong as a 4mm to 5mm mild steel plate?

 

[johnakay]

well put this way I don't think I can buy 4mm plate but 5mm yes in mild steel.
what I was asking is 3mm stainless steel have the same strength as the 5mm thick plate?
that is all that I was asking?
the company who ordered(a friend) the last lot of small brackets had them made of stainless steel,
even though I did ask for mild steel but I'm not complaining as I got them done very cheaply.
so I wouldn't mind if I could get these done in stainless because that is all he deals with mostly.
he does a lot of work for the food industry as well as others.
so they use stainless all the time.
with the above picture rather than weld a plate onto the horizontal plate .
I would like to have it made in one piece .
yours and others advice is much appreciated.
I've been out of steel manufacturing that long I've forgotten what I've learnt off others.
my last job was in manufacturing on a assembly line just welding with no fabrications.
oh and I was never time served welder or fabricator mostly self taught and what I learnt off others.

 

[hotrodder]

what I was asking is 3mm stainless steel have the same strength as the 5mm thick plate?
that is all that I was asking?

Yep you did, i went off on a tangent as Al already covered that with 'depends'. My bad. Assuming the 'mild steel' is s275 then it's min yield strength is higher than say the min yield for 304L
I'm still confused though... I was origionally posting under the assumption that you were currently welding the brackets out of 4 or 5mm mild and wondering about folding them from laser cut 3mm stainless. As the example in the pic is welded and 3mm i'm struggling to work out where the 4 or 5mm fits into all this

Obviously it varies with different companies but if the place your mate uses is anything like the guys i use there's no reason why he couldn't get them cut from a different material to his usual order- i do it all the time, picked up a bunch of 0.9mm CR4 mild steel stuff today along with some 4mm 5083 ally and a mix of 0.9mm & 2mm 304L 2B. Some of it was billed to me, some to my customer as they're a VAT registered retailer and i'm a lazy sole trader that does as little as possible. All the profile cutters care about is their min order of £40 + VAT is met, yes if you can meet that out of one thickness of one flavour of metal it makes things cheaper (economies of scale an all that) but a chunk of that saving can be wiped out if substituting stainless for carbon steel as the former is a chunk more expensive.

Another thing to think about is that welding carbon steel to stainless can result in brittle welds if you don't use a dissimilar wire such as 309...

4mm exists in plate, not so much in strip/flats where, as you say, you typically get a choice of 3 or 5mm. the profile cutters will be using plate so it comes down to what they stock

 

[johnakay]

thanks for your reply HOTRODDER.I'll try and get it made out of mild steel as this will be a load bearing.
don't want it breaking due to brittleness of the weld. thanks.