316 or 309 stick?

Poland308 · Tue Sep 15, 2015 5:26 pm

Got a new project dumped on me need to weld some mounting plates in a SS mixer for a fertilizer mixer. Plates will be 316 SS approx 4in x 4 in. Not sure if it will be welded on like a pad or set up like a tee joint. Tank wall is on 1/8 in and the customer thinks the tank is 316 but it looks more like 304. I've got 316 and 309 stick both are 3/32 rod.
Last time I used them it was on much thicker pipe and flanges. I remember running down around 65-70 amps on the thicker stuff. Any recommendations on what rod and possible amps.

Tank has been flushed out with water but SS is contaminated with nitrate and fly ash from the fertilizer. I think they may also have some ammonia and some patrolium additives they use as well.

Tank is open top and currently on its side for repairs. Ventilation is not an issue but outside and tig is out of the question.

Tue Sep 15, 2015 6:18 pm

Either rod should work fine, but since you know one component to be 316, and the customer "believes" the other to be 316, I think if those were my choices I'd weld with 316. I don't see it going wrong even if the tank is 304.

There may be an argument for using 312, but I'll leave that for the specialty guys and foodies.

Steve S

Poland308 · Tue Sep 15, 2015 7:50 pm

Thanks. I will buy a new type of rod if someone thinks it will help due to probably extreme impurities.

Poland308 · Wed Sep 16, 2015 7:18 pm

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Poland308 · Wed Sep 16, 2015 7:23 pm

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Did some test runs. With beer.

Poland308 · Wed Sep 16, 2015 7:31 pm

I started at about 30 amps and went up in aproximatly 5 amp at a time. Went vertical up and down. As well as horizontal at all possible angles on pipe. Except 6G. Found I started to get a better bead around 50-55 amps. Vertical up needed about 10 amps less to keep from burning through. 309 seemed to run hotter at the same amps. Need some more practice. Did both 309 and 316 theses are just some of the pics.

Poland308 · Wed Sep 16, 2015 7:32 pm

Any advice would help please.

Owr · Thu Sep 17, 2015 12:57 am

Make sure to have the weld area cleaned good - clean more then just where you will deposit the weld so you won`t get nasty stuff burning away because of the heat.

How thick is the base material? - if it is 3mm or more then it is not such a big problem with burning the chromium away on the other side of the base metal, especially when welding vertical up.

The other thing is what type of electrode will you be using in terms of coating? Basic coated produce more heat and it is harder to clean the weld afterwards. Stainless electrode welding requires much lower amperages than mild steel and if you have to lower the amperage a lot you can have difficulties with voltage. Special electrodes run smoothly even on low amperages for welding on thinner materials. Example with an amp controller:

https://www.youtube.com/watch?v=Gr9G-XzRsS4

Rutile needs low amperage for vertical up also because the pool is so fluid that you have to get the balance between penetration and weld consistency just right. For vertical you start the arc, shorten the arc length as much as possible and adapt angle and travel speed accordingly. Think of it as running a wax crayon over a hot surface - you will see the slag deposit evenly below the pool if done correctly.

Best ratio beetwen weld quality and weld characteristics would probably be rutile-basic coated electrodes.