Thread: welding Mild steel rhs to stainless rhs

I will look stupid in a few minutes when the experts come on however I imagine you could do it using .9 stainless mig wire.

I'm gunna stand next to Dazzler and possibly look stupid also - but I also think SS arc rods or SS mig wire would be best.

So it can be done... ????????

I've succesfully welded ms to ss with normal steel rods in a stick welder.
My SIL ,a boilermaker said it can't be done, he was surprised when he saw the finished job. Since then he's used ms rods to weld ms to ss

Blokes

I am not a good welder but I welded a piece of 25mm black round pipe to an axe head using stainless steel rods, that was 16 years ago and the hand axe is still going strong today.

D D

Can be done well with arc, MIG I don't know.

Pop into a BOC Gas 'n' Gear or similar and ask about the rods you need to do the job properly. I've welded the two using mild steel rods and had poor results. I was then advised to use a particular stainless rod (welding mild steel to 304 stainless for car exhaust systems), from memory it was a CIGWELD SATINCROME 309Mo-17.

They also did a 'weldall' product, but I haven't used it.

I,ve welded stainless to stainless , mild to stainless plenty of times with cheap Chinese rods and general purpose aussie rods . Welds like normal , the weld will rust though and a little bit around the weld looses its stainless quality and also rusts

I've welded plenty of stainless earthing points on power poles with general purpose rods. CIG Satincraft to be precise.

Kev.

I've got wia 12p's at home, then. that will do nicly. thanks chaps

will post pics when I've done it.

It can be done, but I don't know what they use. As an example, there are plenty of mild steel balusters welded to stainless handrails.

Tools

Hi Yogie,

Each situation is of course, different but in your case I am guessing it is welding a stainless foot pad that clamps behind the rain gutter of the vehicle it is mounted upon. .

Two forms of corrosion can attack your job in situ here.
Electrolytic corrosion and the usual one from moisture will accelerate the process around the fusion line of the two metals.Mild steel is not an ideal choice as during welding the carbon grains are aligned along the weld boundaries and subsequently will corrode out.

Any where moisture can build up and linger will be a site of potential corrosion.

Initially a m/s electrode will be successful but not in the long term. A stainless electrode, a 309L would be a better choice.
If not grind back the welds and paint to assist corrosion protection.Theres is more here "

http://www.azom.com/details.asp?Arti..._Design_Points

Grahame

I've used .9mm MS to weld stainless pipe to MS RHS. The weld obviously has to be painted.
It is not structural so no idea on weld strength but as a joining medium it is fine. You get a normal weld bead etc.

Originally Posted by Grahame Collins

[...]Theres is more here "

http://www.azom.com/details.asp?Arti..._Design_Points

Grahame

Thanks Grahame. Atlas has some interesting reference material on their site:

http://www.atlasmetals.com.au/Technical_Handbook.asp

"Welding Dissimilar Metals
Welding together of different metals, such as of Grade
304 to Grade 430 or a stainless steel to a mild steel, can
be carried out, although some extra precautions need to
be taken. It is usually recommended that over-alloyed
austenitic welding rods, such as Grade 309, be used to
minimise dilution effects on the stainless steel
component. The composition of the weld deposit resulting
from dissimilar grade welding is shown in the Schaeffler
diagram or its successors by De Long and more recently
the WRC. AS 1554.6 contains a table giving the prequalified
consumables for each combination of dissimilar
metal welds"

A similar chart (presumably to AS1554.6 - anyone got a copy) appears here page 2 - answers for all processes:
http://www.burnback.com.au/helppdf/dissim.pdf

More general info here on welding dissimilar metals from the welding institute:
http://www.twi.co.uk/j32k/protected/band_3/kspw002.html

Guys
Without going too deeply into it ,the requirement for for welding of mild to SS is that the filler material is more corrosion resistant ( more noble) than S/S parent metal.

The welded bead and its fusion areas are subject to corrosive attack along the fusion boundaries.If using a stainless base filler the electrode should bear an L post fix eg 309L.
With Lower carbon content the deposited bead will have reduced chances of of carbon moving into the fusion boundaries and setting up a metallurgical structure subject to corrosive attack.

The other big factor is the environment your welded joint is exposed to. For instance where stair balustrades were mentioned I'll bet that the mild steel was painted up to and just past the weld fusion lines. Little chance of a corrosive effect there,but different on the roof of a car in a drip channel.

In the case of the the car luggage rack I would be seeking to minimise corrosive attack by painting up to the weld and by insulating the rack from the car body as electrolytic corrosion will begin to start as a result of using dissimilar metals in a wet environment.

In the long term a the weld completed with the mild steel electrode will degrade over time subject to mainly to the environment it will be subject to.

The repair would be better attempted by using mild steel bits and pieces and welding with mild steel,but well protecting them with paint and insulating against electrolytic attack.

Grahame