Loft Steel Beams Welding

[gasbusters]

Hi all, ive got a few questions about welding steel beams.

Ive mentioned on previous posts il be doing a loft conversion soon and will be using 5.9 meter steel beams to support floor joists.

The beams are 203 x 203 x 46kg.

Each beam will be spliced into 2 peoces measuring about 1.9 meters each section. They will be joined using steel plates and 36 x m12 sheer proof bolts for each joint.

Now my structural engineer has advised this is suffient but would be good idea to get the joints welded as well.

Now ive just found out an old mate is a welder with 20 years experience welding car exhausts daily. He says he can weld the loft joists for me.

He has advised that the weld they use is stainless steel, and welded using a 1.5mm weld tip around the plates on the beam.

My question is, can you use stainless steel welds on steel rsj's? And would this be sufficiently strong to provide additional support to the loft floor?

Or is there another metalhe should use for the welds? The only other metal they use is mild steelwhich he says would be too weak.

Heres picture of the joints on loft beams

Thanks in advance

 

[Burnerman]

For sure, you can use stainless rods or wire to weld mild steel......but Im not too sure why he would want to do this?
The weld will be corrosion free but may cause the mild steel to corrode quicker - not that this will be an issue in this case.
John

 

[gasbusters]

For sure, you can use stainless rods or wire to weld mild steel......but Im not too sure why he would want to do this?
The weld will be corrosion free but may cause the mild steel to corrode quicker - not that this will be an issue in this case.
John

Sorry im a bit confused, the steel beam/rsj, are they made from Mild Steel?

The welder says ge uses stainless steel on his car welding as its a stronger joint.

 

[Burnerman]

Dont be confused by the term ‘mild steel’ - there are many varieties depending on the carbon content and its as tough as hell!
Your welder is correct - the stainless joint will be tougher and less prone to corrosion, but the surrounding parent metal will still rust. Nothing to worry about in your instance!
John

 

[Burnerman]

Just to add a little more.....with that volume of bolts I wouldnt have thought that welding was necessary here, but thats not for me to say.
John

 

[tony1851]

Your SE would (or should) have designed the splice to accomodate the maximum bending moment at the splice point, so there is no need to weld.
The fact that he suggests welding begs the question: is his design satisfactory as it stands, or is it not?
Site welding is (a) not as reliable as shop welding and (b) can be dangerous, particularly in confined spaces like lofts.