Welding Tips and Tricks

Hi Team

I'm considering fabricating an outdoor firebox, something similar to the attached photo.
I am looking at possibly making it from say 16 gauge Stainless instead of LCS, but am a little concerned about distortion due to the low thermal conductivity of SS.

I obviously don't care about a small amount of distortion while it is operating, but I wanted to avoid major permanent buckling.

I'd appreciate any ideas or suggestion to work through this (extra ribbing, reinforcing, different methods of construction, steer clear of SS etc).

Thanks for any advice

Stainless would look cool, but once you've got a fire going, isn't the metal going to have "HAZ's" all over?
Just curious, are you hand cutting the matal?

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I can't think of any reason to shy away from using stainless other than the additional cost. We use quite a bit of 321 (welded with 347) at elevated temps in the plant as well as 2205 (welded with 2209) duplex. Both of which stay at around 1200-1300* F. But if I was going to use them in your case I'd probably quench the fire with water when I was finished to limit distortion.

If I only had my choice of 304 or 316, I would choose 304 (welded with 308H) 16 guage or thicker for it's abilty to thermal cycle better without cracking.

As far construction goes, I would add 1/4 x 2" flat strap midway up from the bottom as a shelf for a grate made out of 3/8" rod. The flat strap will stiffen the sides considerably and cut the unrestrained flat area down where most of the distortion will happen. The grate will keep the flat bottom from seeing as much heat. It wouldn't hurt to make an X out of flat strap stood on edge in the bottom also.

Once you get all that welded in there you'll not have enough money left for fire wood so it will last forever. If you don't put any vent holes in it you can always get some fish and keep in there.

Len

Braehill wrote:I can't think of any reason to shy away from using stainless other than the additional cost. We use quite a bit of 321 (welded with 347) at elevated temps in the plant as well as 2205 (welded with 2209) duplex. Both of which stay at around 1200-1300* F. But if I was going to use them in your case I'd probably quench the fire with water when I was finished to limit distortion.

If I only had my choice of 304 or 316, I would choose 304 (welded with 308H) 16 guage or thicker for it's abilty to thermal cycle better without cracking.

As far construction goes, I would add 1/4 x 2" flat strap midway up from the bottom as a shelf for a grate made out of 3/8" rod. The flat strap will stiffen the sides considerably and cut the unrestrained flat area down where most of the distortion will happen. The grate will keep the flat bottom from seeing as much heat. It wouldn't hurt to make an X out of flat strap stood on edge in the bottom also.

Once you get all that welded in there you'll not have enough money left for fire wood so it will last forever. If you don't put any vent holes in it you can always get some fish and keep in there.

Len

Thanks Len for your in-depth technical appraisal, guidance, and excellent suggestions. I take your recommendations on-board. All good. I had already thought how I might keep the actual fire slightly separate from the unit, perhaps with a cast-iron fire grate, but I've got some 3/8 stainless bar on hand (316 I think) that I might incorporate into the design.

The use of some flat on-edge is a great idea for reinforcing.

Thanks again for the great suggestions, and I'll figure a way to plug the holes if it ever needs to become an aquarium (!)

Incidentally, I've got two stainless steel billies I made 20+ years ago from some 8" tube with a circular bottom welded in.
When camping in the outback, these stay at the campfire all night. Boiling water whenever you need, but I'm a bit concerned as I think they'll only last about another 400 years.

Thanks again

Trevor

PS:

@Len:

Would you think Stick, TIG or MIG to be the best? (Well TIG is probably the best, but would Stick or MIG be successful also)

Trev

Well, since you aimed that question directly at me, I would Tig it but not because "it" is the best process, but because I would garner the best results from it. Not only on this forum but I've seen firsthand what in the hands of a capable welder can be done with both stick and Mig S/S.

In all honesty it would be better to get some responses from other members who deal with thin stainless every day. I have a lot of stainless throughout the plant but it's usually Carbon steel that provides most of my welding jobs. I have a lot of older piping that's in service that has low pH moisture in it that no metal really likes so we just use Carbon and replace it often.

Len

Thanks Len,

Good suggestion to ask the question to the wider forum.

Any recommendations from the SS guru's on this project?

Thanks
Trev

As far as stainless, I don't know, but I would consider something a little heavier than 16 gauge. I build a lot of fire rings and am working on a fire pit. Something like that would hold a lot of heat since the wood is resting in the box. Just a suggestion.

@Matt,
One thing that needs to be considered when you're dealing with stainless is price. Locally a 4'x8' sheet of 16 gauge (.059) 304L is around $390 and about $810 for 11 gauge (.120). I like the idea of a stainless brazier, but not to the tune of $1000 T & M.
16 gauge at least cuts that in half. I know you can use drops to save money and that would be the only way I'd even think about stainless.

The OP asked if there was any reason to stay away from stainless, that would be mine, as stated.

Len

On 16 ga stainless, I'd stay away from stick, simply because I find the heat hard to manage relative to MIG and TIG. My experience with stick on stainless is almost all 1/4" stock and above, though.

I'd think you'll get excellent results with either MIG or TIG, with the choice being left to which one you're more comfortable welding thin material (and with the stiffeners, thin to thick material) with.

Steve S

I deal with 16g daily it may be a little flimsy..I'd look at 13g if it was my job a lot more sturdy. Tig be my choice....it will look beautiful and allow the best control of heat input. I would also add support braces across, I'd use around 40-50 amps with 16g and 60-65 with 13g, clamp it to the table and clamp a piece of alum or brass behind the joint to prevent sugaring and control heat.

I like the idea, might do something like the photo you posted myself!

Well, after a lot of umming, I changed approaches.

I had a thought that SS might look a bit too 'clean' for an outdoor fireplace. So went for 2.1mm tread plate instead, but with a stainless grate:

Overall, I think it was a better decision. Thank to everyone who contributed ideas and suggestions.

Ranger

I like it...turned out very nice!

That is quite nice, I like the diamond plate look.

Len

Thanks Len and Rick
Yep, I'm much happier with the finish

Ranger,
Very nice! I can tell there was some thought and a plan involved. You didn't just slap something together. I like it.
-Jonathan

People pay big dollars for that kind of stuff at Bunnings. Nice work.

Mick

This looks great!
I'm making a similar one for myself and wondered what the purpose of those holes were for?

Kentweld wrote:This looks great!
I'm making a similar one for myself and wondered what the purpose of those holes were for?

The holes allow air in, thus keeping an oxygen supply available to the fuel. Otherwise, it would just smoulder.

Trev

Awesome work and design.

My wife has been on me to make a fire bowl/pit for our new house. I showed her your finished brazier and nearly busted my eardrum in excitement.

Looks like I'll be copying your design.

Thanks Chris
Go right ahead! I forgot to mention that the top section 'keys' into the square hole in the base, and is removable. The base can be inverted and inserted into the top section for compact storing.
Trev

Did you use tabs or a plate for the key?

I just used 4 corner tabs, cut and folded 4 right-angle 'L' brackets from a strip of the diamond plate, and welded one into each corner.

Trev

Very nice project, with great results! Great work! I will be showing this to my students!

Good idea in the end; going with the stainless grate and carbon body.

For my back yard, I dug a hole, threw wood into it and used the money I saved to buy liquor.