Welding stainless steel

[michael_99]

I'm in the prosses of making a windvane, and have come up against a problem. I have made a bracket in 304 steel, (free) to hold the oreblade, and welded it ok. I was given two old rudders off a cat or something, with a long stainless tube, which I had hoped to use, to connect the ore to the rest of the set-up . The tube was the right size, and free, so I thought I was lucky. However, it would not weld, it just blew holes in the steel. Having just got a copy of PBO april issue, yes, here down under we are 1 mth behind, but still, it gave me some insight into my problem.Could the tube be some other form of stainless, I thought it was 316, but no. Looking at the cut end, it appear to be two tubes put togeather. No one could tell me what kind of steel it was.
I hope, as always, someone can shed some light on this problem. Lookign forward to the may issue of pbo, welding ss.
Thanks.
Michael. /forums/images/graemlins/confused.gif

 

[supermalc]

Another long shot I'm afraid, but just trying to help. I have successfully welded stainless with an ordinary stick welder and normal steel rods, so I doubt this is your problem. If the tube is brass, or ally this will be your problem, but if it is steel, it could be that being made of two separate tubes it is simply too thin, or the welding power is too great, hence your 'blowing holes'.

Sorry I can't be more specific.

Scroll down this page and you will see a picture of the gear lever I made, when I rebuilt this motorbike in 1983. Stainless bar aquired from work, I welded it at home with a small aircooled stick welder and normal mild steel rods. It never broke.
http://www.angelfire.com/rnb/malcsworld/bike/mbphotos4.htm

 

[mirabriani]

I was taught that the most important thing is to
make sure the welding rods are,as far as possible, the same material as the item to be welded.
I suggest you ask an expert welder.

 

[Graham_Wright]

When stick welding thin stainless, I have used a backing block of something like brass. I have no idea what the metallurgical consequences may be but it does stop blow through and the welds seem secure.
There is a spark test to distinguish between the three common grades of stainless i.e. 303, 304 and 316 but I find it impossible to find significant differences between the various fireworks.

 

[michael_99]

Graham, the tupe is double wall, is a rudder sharft, could that hold the clue to the mistery steel. The wall is thick. Could rudder sharfts be made of something other then 316 SS. According to PBO april issue, SS fitting for under waterline application, 316 is not the best.
Looks like I just have to go and buy some, if I can find someone willing to sell me a small piece, and not 6 Mtr.

 

[norseman]

Try www.Mallardmetals.co.uk, they sell all types of metal and in small sizes for model makers and bike restorers. the prices are reasonable to. The spec they sell is 303 but they can do others on request.

 

[michael_99]

thanks norseman, but I'm in Australia. /forums/images/graemlins/smirk.gif

 

[nedmin]

Have you thought of brazing it. If you can get some eutectic rods which have a silver content, and you can use these with a butane torch. They are a flux covered rod. They give a very strong joint.