Gas forge help/advice/

[Shoshinjoe]

Hi all,  so I am thoroughly enjoying my gas forge so far but I have a question regarding how the run.  I am so new to this I am still reading as many posts on here as possible and reading through the forges and burners 101 posts but haven’t found an answer yet.

So image 1 is as the forge is fairly hot but only been running maybe 15 mins. Should I be adjusting the oxygen or pressure to increase the size of the blue flame or decrease?  What effect does that have?

The next image is from the side just after the first pic.  Even though I’ve been reading about the difference between carburising, neutralising and oxidising atmosphere I still don’t really know what I am looking for.

 

And finally this last pic a after about 30 mins.  It looks to me like the flame goes weak all of a sudden.  Is this normal? What is it?

 

specs:

single Venturi burner - opening is just over an inch   "Commercial links are a violation of TOS"

volume of forge is 108.07in3

not 100% sure what psi I’m running but my valve goes from 0-20 and it’s about half way

Cheers

Edited March 5, 2020 by Mod30
Commercial link removed

[Latticino]

Extremely small gas forges, like yours, have tuning challenges also.  Your choice of a burner with a 1/2" mixing tube was likely prudent.  The burner manufacturer recommends a forge with internal diameter on the order of 6" (and an internal volume of 215 cu in, yours is around half that).  This may relate to the optimal flame development length.  In a shorter forge you may need to adjust this flame length with a change to the burner outlet (perhaps considering some form of multi outlet port system).  It is really hard to tell what is happening because digital cameras don't accurately depict colors of incandescent sources.

It is also hard to judge whether your forge is operating in the lean, neutral, or rich range from these pictures with so much ambient light.  If you take a photo from the side in low light we could more likely see the exhaust gasses/dragon's breath exiting the door.  I suspect that you are running a little lean and will need to close the air gate a little.  I like to see around an inch or so of dragon's breath leaving the forge to ensure I'm in reduction to limit scaling and decarborization.

Another issue you may run into with this small a forge is that the tip of the flame will create both a hot spot and a local oxidizing zone.  Ideally you don't want this directly impinging on your blade stock.  You forgings are looking very clean though (nice job there), so it may not be a problem.

What is your forge wall constructed of?  If a monolithic castable refractory insulation it may take a good while to fully heat up.  Once it does, the radiant light inside the forge will make it very difficult to see the burner flame, but this should not be a worry.  Listen to the sound of the burner to confirm it is still operating correctly.  Don't ignore sputtering or popping.  Often once the forge walls have come up to temperature you can turn up the burner to an even higher output (if you want to get to forge welding temperatures for example), as the flame front speed changes with changing heat and radiant energy output in a hot forge.  If you are looking for more heat I'd also consider inclusion of some form of rear door.

[Shoshinjoe]

Thanks Latticino.  The forge is k26 bricks coated in duracast refractory about 1/8” thick.

 

my workshop is a tiny open shed in the backyard of our unit.  Will be moving out into our farm sometime this year into a proper workshop.  But I will get some better pics today 

Also I have a brick blocking 3/4 of the rear in those pics 

[Shoshinjoe]

 Latticino should my burner be getting this hot?  

it is set maybe 3/8” to 1/2” into the brick

 

Edited March 6, 2020 by Mod30
Remove @Tag

[Latticino]

Hard to tell what I'm seeing in the photo. The burner mixing tube doesn't appear to be getting hot to my eye, but you look like you are having some local distortion of the forge skin.  As that skin appears to be the only thing that supports the burner there could be a fairly considerable torque on that joint and with a little heat it could easily bend the thin skin. A misaligned burner can cause you problems with heating of the transition betweent he burner outlet and forge insulation.   If we are looking at the outside front of the forge during operation you certainly have heat leaking out of your forge in a sub-optimal location.  I would set the burner further into the soft brick exterior and make sure the forge opening just barely covers the thickness of the burner outlet, then flares out slightly as the opening  progresses to the forge interior.  Be careful as this might encroach on the ideal flame length the burner manufacturer advises on.

Is the photo taken at high or low fire?  Flame front speed does vary based on internal forge temperature, and the existing burner outlet seems quite large.  The abrupt change in size will slow down the fuel/air flowrate from that in the mixing tube (which is a good thing IMHO, as it provides a clear demarcation in flow velocity to aide in system balancing).  However the outlet might be optimized for a certain fuel/air mixture flow and not give you as much "turndown" capability as you might want.  An old school flame retention nozzle with multiple ports made of lots of short pieces of small diameter steel pipe at the outlet might work, but it is hard to tell without some experimentation.  Dudley Giberson (Joppa Glassworks) makes a wonderful burner head that might work better for you, but you will have to coordinate your burner output with the burner block capacity: https://www.joppaglass.com/burner/mini_square.html.  I'm a big fan of castable burner blocks for forges, glass furnaces and glory holes.

In any case I would certainly make a more robust setup for supporting your burner.

To your question, I typically like to see only a very small difference between the opening in the forge body and the burner outlet.  You are only trying to block the radiant energy from the forge interior from heating the front edge of your burner.  Ideally the fuel/air flowrate will cool the balance of the burner (but you do have to be careful when either turning down from high fire or restarting your burner after a short break...).  Your flame front should start just inside the forge, not inside the burner head.  This is one of the more difficult things to tune.

[Frosty]

I'd like to offer ideas but I can't tell enough about your burner to even speculate. Did you make it or is it a commercial burner? If commercial you can tell us the name without posting a link. That way I can see what you have. 

A couple more pictures would be good too. A pic of the whole burner, I can't see what the air port looks like and another of the outlet nozzle will give me an idea of where to go. 

The forge looks like it's getting reasonably hot for the configuration though it could be hotter. 

Frosty The Lucky.

[Latticino]

Frosty,

It is one of those commercial Gameco burners like this one:

[Shoshinjoe]

Thanks again Latticino for the advice,  and thanks for sharing that picture.  And yep so the skin is lifting but it isn’t moving the burning is sitting flush with the recess in the brick.  The orange colour in the pic is the bottom of the outlet.  Also yep it is definitely a heat leak.

I don’t really know what you mean by high or low fire.

Frosty, I’ve figured out the tuning now so I am getting yellow hot inside, but not quite to welding temps yet.  That large chunk at the bottom of the bottom that is the outlet nozzle.  The opening is 32mm, 1 1/4” roughly.

 

Thanks again guys.  I will re-read these posts and provide some more pics of the burner.

[Shoshinjoe]

Those burner heads look great thanks for the tip.

i will build something more robust for the top and to hold the burner over the next week.

the pics at the start of this thread is what I was concerned about. When I start forging  the flame is inside the forge.  But what I think is happening is that as the roof heats  the burner gets hot and the flame changes or moves.  And that is the third picture in the original post.  But that is just a guess I am very green when it comes to this stuff, I just want to learn, it’s all fascinating.

[Latticino]

Actually your current burner nozzle looks much better than I expected.   It appears to have a flame retention ring, which should help with tuning (providing a abrupt change in flow velocity at the burner exit allows for easier tuning to keep the flame front from the inside of the burner in my experience ).  I think your current issue is with slight misalignment as the nozzle enters the forge and incorrect geometry of the opening in the forge.  Study the Gibberson burner block design to see what I mean (same site0. Yours should be similar, but cylindrical.

You may also want to contact the manufacturer for tips on tuning.  Looks like the orifice location is adjustable, and that type of burner is quite subject to performance change based on nozzle location.

[Shoshinjoe]

Thanks a lot for all your help, I’ve learned a lot so far.

[Latticino]

Very nice to be appreciated. It is for folks like you that I spend time trying to help.

Good luck.

[Frosty]

Okay, I've seen the burner, they'll work fine, you just need to learn how they work so you can manage the fire. No bid thing, nobody's born knowing this stuff everybody had to start at the "What's this?) stage. Don't sweat it we'll get you up and running.

Latticino is more familiar with this type burner but I'll tag along if you don't mind. 

Frosty The Lucky.

[Shoshinjoe]

My thanks again guys, it is really appreciated. As I said I’m getting great forging temps and my work rate has increased incredibly because of that

 

My my only goal now is to figure out how to tune it so I can get to welding temps.  I really want to make some animal heads and fire pokers and just practice forge welding

[Binesman]

Do you use any kind of an IR?  If not go get some plistex/matrikote/itc100.  It will raise your max temp by a good bit and probably let you hit forge weld temps.

[Frosty]

You're reaching mid yellow heat, it'll weld now you just have to learn how. Easy peasy, just part of the learning curve, time to take your next step. 

I heartily endorse using a kiln wash for a number of reasons but I discourage using ITC-100 it isn't intended for what we need. At one time it was about the only kiln wash known to the blacksmithing community so we used it. There are much better products for what we need and they're less expensive. Plistex and Matrikote being high on the list of effective for the $. 

ITC-100 is a release agent intended to keep bad stuff from sticking to the inside of furnaces such as preventing glazes from fusing pottery to the inside of kilns. It's a top notch product, just NOT for gas forges.

Frosty The Lucky.

[Shoshinjoe]

Thanks frosty I’ll have a look into plaited or matrikote.

Any chance you could elaborate on the forge welding process at mid yellow.  Friday I tried a few different thing in attempt to weld up a rams head.  I tried lots of light taps several times.  And tried a few heavy blows also to no avail.  

Ive forge weld a high carbon but into a tomahawk head in my charcoal forge but that was more of a fluke than actually knowing what I did

Binesman I don’t but will look into plistex or matrikote,  thank you

[Frosty]

I can tell you how I'm most successful forge welding in my gassers. 

Like any welding there are 3 rules: Clean, CLEAN, CLEAN!    I brush then file or sand the join surface if possible, the shinier the better. If it's a billet I sprinkle a LIGHT dusting of flux between layers before wiring, banding, welding, etc. I drop a little flux rock on top of the billet as I put it in the fire and as soon as it melts and flows I flux from the outside. I still don't understand waiting till the steel is orange hot where oxidization is happening at a fast rate.

Anyway, I use flux to keep oxy out of the joint so it can't form scale rather than to clean crud out. I clean it before I put it together so there is NO CRUD to clean out. My joints don't need to squirt molten flux out to carry off scale, or anything else. All the flux does for me is form a prophylactic barrier so hot steel and oxy can't come in contact. Flux is NOT glue, it doesn't stick steel together it just cleans and protects it during the process.

I like to bring my billet up to heat slowly so it's less likely to burn edges and corners waiting for the center to come to welding temp. Once the billet is high red or mid orange I turn up the fire. When it's to temp I give it a few minutes for heat to soak to the center. I don't know how long, I've never timed it, then again not all my welds are successful. Hopefully someone will chime in, there is a well known length of time per inch of thickness for heat to equalize ad that's the soak time.

So when it's to heat I take it from the forge, hold it slightly above the anvil face and give it heavy but slow blows. I don't want any rebound or snap, either can cause layers to shift or bounce apart. I start in the center of the billet and alternating overlapping blows to the ends. By alternating I mean: Center - Close end, - Far end. That doesn't mean go straight to the ends, it means work overlapping blows to the ends. 

Do NOT stop and try to decide what to do when you take the billet out of the fire! Time for thinking and planning is OVER, it's time to strike and don't waste time. Don't hurry but don't waste time, whap whap whap. NOT whap, position, aim whap. You only have so much time and the anvil is eating your welding time every second it's touching your work.

Once the weld's set you repeat the process from fluxing when hot a couple times to refine the welds BEFORE you strike the billet on edge. WELDS plural did I say? Ayup, every joint surface on every layer is a weld of it's own. Stacking a bunch of layers doesn't magically turn them into one weld. One process but multiple actions. 

That's how I do it. 

A simple cross over type lap weld is about the same, I get things positioned and shine it up with a file or sand paper before closing it up. Then heat, reflux bring to welding temp and set the weld. brush, reflux, reheat, rebeat, repeat a couple times to refine the weld.

It's almost all about technique, more so than a specific temperature. I watched a couple farriers have a friendly welding contest. both guys were welding at mid red temp with the old discontinued formula Swan and Easyweld fluxes. What they both had in common was how hard they cleaned the joins. 

Frosty The Lucky.

[Shoshinjoe]

Frosty! Thank you.  I think my issue with the rams head then was not cleaning the joint well enough.  I’ll have another crack at it asap

In terms of lap weld or animals head, do you bend the steel close to its desired fold then clean and fold it fully, before fluxing and welding?

[Frosty]

Close, I bend it close with just enough room to get in with a thin file then I flux it and close it below red heat. Borax base flux melt at about 230f before steel starts oxidizing quickly. A light wipe with an oily rag, clean oil I use 3 n 1 will stick flux so you can close it cold. The only reason I flux it after it's closed up is because I'm over cautious and I don't want any chance for air to get to the join surfaces.

Here's a trick I picked up from a jeweler friend. If you need to flux really tight spaces, say cable you've cleaned well. You can mix borax with water and it'll penetrate. As you heat it the water will evaporate except that which has become part of the borax molecules which needs to get to boiling temp to escape. Well, when the water boils the borax foams and the pressure forces it into everydarned thing. 

The trick is getting cable clean enough internally for this to work. Leaving the cable oily usually fluxes it just fine but you have to KNOW there are no plastic stress bands or core. Plastic is B_A_D_N_E_S_S!!! Not just for the weld it releases phosgene gas, look that up for some scary dreams. 

Frosty The Lucky.

[Shoshinjoe]

Oh man, thank you.  I’ll have a go at this tomorrow and let you know how it goes

[Binesman]

Forge welding is an interesting thing.  I've heard dozens of tricks from hundreds of smiths FAR better than myself.  The best advice ive ever heard for it though is this.  "Find what works for you and focus on improving that"

[ThomasPowers]

My first forge welding class, a 2 on 1, with an ABS MS as instructor back in the early '80's; I still remember him yelling "Don't look at it HIT IT!"

I also teach my students "Don't take the piece out of the forge until you are ready to work it at the anvil!"

[Irondragon Forge ClayWorks]

Ike Doss used to say that to me all the time.and now I have to repeat it to my wife but she is a faster learner than I was.