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I Forge Iron

Checking what I am watching-Forge Welding


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I need to clear up some contradictory statements.  This regards forge welding.

In a video by Calerin Forge He says you want the metal heated to the point of sparking and sounding like bacon when it comes out of the fire before welding.  In a video by Paul Sorrels he says you want to just see sparks jumping.  In another video that I cannot find again (a small group of people in England take blacksmithing lessons and make some gates at the end) the smith says sparks jumping off the metal means it is burnt and good for nothing.

In reading things here I have not found a mention of sparks jumping off the metal before welding.

Can someone straighten this out for me?

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It depends on the alloy.  Sparking is considered too hot for most high carbon steels and just right for real wrought iron.  If someone specializes in once area and the alloys used there they might not take in account other areas with other alloys..  Now stop looking at videos and go visit someone who can work you through it a couple of times.

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It's an art meaning everybody comes to their own terms with the metal. However there are some pretty solid constants. Getting the work sparking hot is okay, sometimes necessary IF you're working with wrought iron. However if you're working with steel sparking hot means it's burning, a shower of sparks to a hissy crackling sound means the steel is on fire, burning like a match. This is a B-A-D thing.

Getting steel into the high yellow temps you get to the point where the carbon starts burning on contact with atmospheric oxy. this is commonly called "decarbing"(?) the steel and can occur below sparking heat. When you start seeing sparks it's because the steel has reached it's boiling temp and the little bits of spatter are burning on contact with oxy.

It's not such a big deal with wrought iron, there isn't enough carbon in it to alter it significantly if it reaches the ignition temp for carbon. Any iron oxide generated at sparking heat is no big deal, there's enough silica in it to self flux and it just welds into a more refined bit of iron.

Let's hope I didn't muddy the slack tub.

Frosty The Lucky.

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In my experience, sparks jumping before welding will make fluxless welding (coal forge) exponentially easier for mild steel or wrought iron. However, if you are working with HC steel, you will be drastically reducing the carbon content of the steel, making its purpose either useless or drastically less effective. If you are fluxing mild or wrought to weld you will find that high of a temperature excessive as it is much easier to weld at a lower heat with particular fluxes. Iirc Brian Brazeal has a video of him welding mild steel with iron mountain flux at an extremely low heat. The strength of that weld is obviously debateable but the point is that you can get steel to tack at low heats but it would still take more subsequent welding cycles to ensure a strong weld. What steels were being welded and to what purpose in the videos you are talking about? 

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 There is a guy on the board here 130 or so miles away.  If I get the time I'll see if he is available.

 

Frosty, That made sense.  Will different alloys spark at different times?  In Walter Sorrell's case he was laminating a piece of high carbon between softer.

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There are a number of guys onboard in Utah and Arizona, I'll bet less than 130 miles. Then again what's 5+ hrs driving to solve a problem and spend time with another blacksmith? I've traveled 10x farther than that.

I'd imagine different alloys react differently to most anything but it's going to take some testing to find out what acts how. I judge welding temp by to be at "sweating temp" or watery heat. The surface appears to have a shimmer to it like light flashing across water, it looks wet. If I let steel get to sparking heat I've screwed up but that's just how I do it.

I clean, SHINY clean and flux the joint before I heat it. The hotter the steel the faster it oxidizes so I flux and close the join as cool as possible. Light on the flux, it ISN'T GLUE! Good flux is a joy.

Set the weld with gentle dead blows, brush, flux, heat and refine it. Repeat a couple times. I test the set by laying one side of the joint on the anvil and see how it cools. If there's a sharp differential in color at the joint it isn't set. Brush, flux, heat and do it again. LIGHT, dead blows. Test and proceed as indicated.

Frosty The Lucky.

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"like butter melting in the sun"  was how it was originally described to me.  Also, besides cleanliness (which flux helps), if you are having trouble getting a good stick go hotter and don't hit as hard!  Billy Merritt demos forge welding sticking the weld using a hammer handle!   Too hard and it "bounces" the piece apart---what I tell students "a firm tap not a sharp one"  (see why being there in person might help make sense of these instructions?)  I had my first lesson back in 1984 in a 1 on 2 with Jim Crowell.  Billy Merritt really helped me tune up my forge welding at a IBA conference some time later.

 

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Thomas and Frosty,

Thanks for your expert comments.  I have read up on forge welding many times and not gotten quite what the author meant.  Your descriptions clicked and I can match them to what I have seen in my forge.  I keep going past the watery/melted butter and in to the sparkler range and my weld aren't very good (land look nasty).  Again many thanks.

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"looking nasty" is generally indicative of over heating and/or heating past the point where the flux can protect the metal. (a certain amount of flux can only "eat" a certain amount of "crud"  keeping on producing oxides after the flux is full up causes problems too!)

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I'm in the no flux forge welding camp and very definitely do weld with sparkling (but not burnt) mild steel. I've learned how to judge the sparks from the fire so that my welds don't appear pitted.

My method in a coke fire is:
Get the coals white hot, metal goes in, medium amount of air to maintain fire temp, choke off air frequently to check for sparks popping, when I see sparks that pop choke the air off completely and count to 8. If the sparks continue to sizzle out of the fire until the count of 8 then I know it's hot enough. If the sparks die after 2 - 3 seconds then it's not.

I recently killed two birds with one stone when I wanted to test the strength of my forge welds and also needed a handled to pull my workshop door closed. I found to pieces of scrap 20mm solid square bar, scarfed them and welded them together. I then twisted the weld loads and bent it a fair bit - didn't break and the scarves didn't peel up. FYI I don't like the aesthetics of this handle, it just served a quick purpose. Will upload pics separately as they are on my phone.

Pic 1 - half way through welding, pic 2 - completed weld, pic 3 - handle.

 

20151124_162706.jpg

20151124_163624.jpg

20151124_184245.jpg

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Sounds like sparks are an important indicator.

Maybe with wrought you can get away with lots of sparks.

But sparks say "I am hot enough to weld"   Maybe...   Too Many sparks is a waste or disaster...  Too few sparks maybe not all is hot enough?

I am just interpreting. and trying to summarize what I am reading and have seen...   My experience is not great...

Sparks need to be seen with the the metal in the fire.   You have to see those metal burning sparks coming up from the fire with the metal still in the fire.   You can't just be pulling it out to look all the time...

Flux is there to prevent O2 from getting to the metal to create burning.   Flux blocks the O2.   It is there to prevent the FIRE triangle.  

Seems like excess sparking is always bad but maybe with wrought it is not so important because you are not worried about carbon?

 

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Solid Phase Welding is like a 3 legged stool:  Temperature, Cleanliness and Pressure.  Max any of thes out and you can get a weld

Forge welding is mainly temperature

Vacuum welding is mainly cleanliness

Explosive welding is mainly pressure

I've seen forge welds done at temps I would consider on the low side for forging! But the demonstrator was an expert.  

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"Buttery yellow," Good descriptive phrase, I'll have to remember it.

Borntoolate: I think you have it about right, like so many things in life it's a matter of quantity over quality. Sparks themselves aren't the issue, how many is what counts. Judging how many is a matter of experience and that will vary depending on different factors. Mostly forge type, fire management and possibly alloy.

I've seen beautiful welds demonstrated at medium orange. By beautiful I 'm referring to the integrity of the weld not the look. Once welded the smith literally hammered it cold till the base metal broke. The weld remained competent. It was a heck of a demonstration, the fellow is or was a farrier in addition to a professional smith.

Frosty The Lucky.

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Before the web, when self learning, I had to rely a lot on books. The author, Ernst Schwarzkopf,* has a good chapter on welding. The British book, "The Blacksmith's Craft" has a succinct portion on fire welding, and Harcourt's "Elementary Forge Practice" has excellent drawings of scarfs. The British book talks about three welding heats. For certain grades of mild steel, the recommended heat is "light welding, sweating, or slippery heat." This is just above a yellow or lemon heat which is the optimal forging heat for mild steel, not for welding. The metal is a yellow/white and the surface may appear sweaty due to surface molten flux and/or scale. When I teach, I call it a sweating heat, and with flux, I use it quite often. A "full welding heat" occurs when a few incipient sparks begin to appear above the fire. This heat can be used for mild steel. The sparks are particles of metal separating from the parent stock. Too many sparks however, cause burning and pitting of the steel. Too much oxidation. "White or snowball heat" is used for welding wrought iron, but is too hot for welding mild steel.

When working mild steel, I frequently use the sweating heat as it is safe in terms of burning the metal. The disadvantage is that the heats don't last as long as the full welding heats. I have been known to take a few sweating heats over the same area to insure solidity and to get rid of shuts. We often read that wrought iron can withstand the bright, "white" heat, but wrought iron can also be welded at a sweating heat. We must not forget that high carbon steel was welded into the wrought iron bodies of axes, adzes, and chisels This heat was used to preserve the steel and not ruin it.

*Plain and Ornamental Forging, Ernst Schwarzkopf

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  • 7 months later...
On 1/8/2016 at 6:51 PM, Frank Turley said:

Before the web, when self learning, I had to rely a lot on books. The author, Ernst Schwarzkopf,* has a good chapter on welding. The British book, "The Blacksmith's Craft" has a succinct portion on fire welding, and Harcourt's "Elementary Forge Practice" has excellent drawings of scarfs. The British book talks about three welding heats. For certain grades of mild steel, the recommended heat is "light welding, sweating, or slippery heat." This is just above a yellow or lemon heat which is the optimal forging heat for mild steel, not for welding. The metal is a yellow/white and the surface may appear sweaty due to surface molten flux and/or scale. When I teach, I call it a sweating heat, and with flux, I use it quite often. A "full welding heat" occurs when a few incipient sparks begin to appear above the fire. This heat can be used for mild steel. The sparks are particles of metal separating from the parent stock. Too many sparks however, cause burning and pitting of the steel. Too much oxidation. "White or snowball heat" is used for welding wrought iron, but is too hot for welding mild steel.

When working mild steel, I frequently use the sweating heat as it is safe in terms of burning the metal. The disadvantage is that the heats don't last as long as the full welding heats. I have been known to take a few sweating heats over the same area to insure solidity and to get rid of shuts. We often read that wrought iron can withstand the bright, "white" heat, but wrought iron can also be welded at a sweating heat. We must not forget that high carbon steel was welded into the wrought iron bodies of axes, adzes, and chisels This heat was used to preserve the steel and not ruin it.

*Plain and Ornamental Forging, Ernst Schwarzkopf

So, you would use a "sweating heat" or "full welding heat" (properly fluxed) to weld high-carbon steel to wrought iron? (I'm assuming snowball heat would be too hot for the HC.)

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I was taught to take it out of the fire when I observed the first spark but that applied to relatively thin mild steel.

Cleanliness is a virtue but how do you get it clean when you are folding over? Say when making a dragon's head or similar stuff. The folding back creates scale that there is no space to remove. I rely on flux to take the oxides out and it works.

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When folding I bring it close then file the faces clean dust it with flux and close it up preferably at or bellow red heat. That way it's clean and fluxed ready for the next heat, as it reaches orange I reflux it and proceed to weld. It's a technique thing with me, I never did get why so many folk heat their iron/steel to orange before cleaning and fluxing, orange heat seems to be the temp it scales the fastest. Dust it as soon as it's hot enough to melt the flux and it can't scale. I don't need flux to carry ANYTHING out of the joint, it's clean. The fluxes purpose is to provide an air barrier so it CAN'T oxidize.

Of course that's just me.

Frosty The Lucky.

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2 minutes ago, Frank Turley said:

Yes, a sweating heat only for high carbon steel. No sparks. Otherwise, the high carbon steel will crack, crumble, or separate into two or more pieces.

Thanks. I'm thinking about making a san mai knife with an HC core and WI cheeks, and this should help.

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On 1/4/2016 at 11:22 AM, natenaaron said:

Yeah yeah yeah but it is a couple hundred mile drive one way.

couple hundred mile drive from someone who'd done it?  Not hardly..that is if you are up where I think you may be...

 

JPH

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