Filler Metal

309L will help tie up the carbon and prevent loss of corrosion resistance of the 304.

The first choice will be flux cored SS wire AWS A 5.22 E 308L T1. Advantages are , it could be used with low cost CO₂ gas (100%) or Argon-CO₂ mixture (25%CO₂)with 20 LPM to give a good shielding. You can select 180-230 Amps, 25-27 Volts, 40-50 cm/minute travel speed, 12-15 Stick out etc.This high travel speed gives the required fillet leg of 6-7 mm and lower heat-input to avoid distortion in the joint.

Alternatively AWS A 5.22 E 309L T1 could also be used but, may not be necessary for your weld joint.

Any increase in Amps and Voltage selection will have correspondent increase in travel speed and helps to reduce the heat input further.

The second choice is AWS 5.9 ER 308L, but requires expensive Argon (pure) or Ar-O₂ mix(2%). The travel speed will be avg. 30-35 cm/min resulting in higher heat input compared to FCAW process. Further solid wire can not give same good ripple factor and finish like in Flux-cored SS wires.

Trust above details will help you to make your choice.

Sridhar.

I thank you all for your insight and assistance in this matter. I will update during fabrication to let you all know exactly what and how we have progressed. If anyone else has a few cents to throw in the pot they are always welcome. Thanks again.

Well, we have changed base material to A709 Gr35 and A709 Gr50. We will be ataching the stainless flat bar to this useing a 1/4" fillet weld.This process needs to be as corrossion resistant as possible( it will be painted and spend its life in water). So is the 309L still a good choice? It seems good to me especialy with useing Co2. Does anyone see a problem with this? I know I will have to write a PQR and have it tested, just trying to pick your brains first.

309L is pretty much the generic answer to stainless to carbon steel welds so I'd suspect that you're still good.

There are few points you have to sort out before putting it in PQR. You have mentioned of suspending it in water. Is it sea water or tap (sweet) water. If it is going to be sea water avoid using CO2 gas.It may create corrosion to the joint in a long run. Prefer pure Argon (or) Argon with 2 to 3% O2 as it will have a long life. It will work out well for ordinary water also and a safe bet. On the other hand, if it is a sea water, the filler wire could be a nickel based alloy like Inconnel or so. This alloy has 60-70 % Nickel and resists corrosion in any form and better than 309 which has around 12% nickel. It is available as a coated electrode and also as a bare filler rod for TIG/MIG processes. Sridhar.

It will be submerged in plain old lake water(no salt). So i'm thinking your suggestion on using the 309L will be the route we"ll take, thanks again for the help.