Heat time for custom built forge

[Deep Forest Tinker]

Hey all, 

I'm self-teaching so i don't have a great reference point for how heating times should work because i cant really watch anyone do it live

I built a charcoal forge of my own design and i think it works pretty well, seems to get plenty hot because it's started melting the firebricks and it can get steel rod up to pretty hot (i'm forging outdoors without a hood so i figure dark orange in daylight is pretty hot?)

I -think- my forge works pretty well but I want to know how long metal should take to heat up. i feel like with the 5/8" rod i was trying today, it took about 10 minutes to get to first hammering temp, then it seems like several minutes in between. 

Is that reasonable? how much time hammering vs. heating do you spend? 

[C-1ToolSteel]

As far as heating vs hammering goes, that all depends on what kind of heat and what kind of hammering. 10 minutes is a long time, but for charcoal, it isn't so outrageous as it would be for coal. In between forging, it probably takes 20 seconds for me to heat 5/8" round to a bright orange heat. I highly recommend using coal if you have acces to any. Charcoal is good for learning, and I've seen impressive things made in a charcoal fire, but if you try real coal, you will never go back. Look on Craigslist. Sometimes you can find it really cheap there. Even free. Just buy a little bit before you buy a whole truck load, so you can make sure it burns well.

[Deep Forest Tinker]

C-1, thanks for the info. I actually have access to coal from a farrier's shop a town over. Charcoal is just much easier to get.

I've read they burn at the same temperature so i can't figure out what the difference would be. is it the density of the heat? I lay my workpiece on the top, should it be stuffed down in? I never know if that ends up making ash stick to it.

This stuff seems harder to find in a youtube video, you know?

[Latticino]

Heat transfer in a solid fuel forge environment is primarily by means of radiation.  The white/yellow/orange... coals (of whatever source fuel) send their heat to the stock by radiating the energy over to the metal.  Therefore if you have your stock surrounded by the glowing coals it will get hotter faster.  Even if the fuel at the top of the arch isn't radiating in the glowing range, it is still radiating heat, and the taller heap of fuel also has an added effect of providing some insulation for the hot zone of the fire, which conserves on fuel use (the back side of the fuel arch).  For coal fires one of the more optimum configurations is a "beehive" arch with an opening in the side for your stock to get heated in.  Properly used it can also help with reducing scaling, by both limiting the amount of air needed and keeping your stock out of the oxidizing zone of the fire.

I have not forged much with charcoal, but understand that it burns quicker (heat content of the material per unit volume) and sends up more ash.  Typically slightly different forge configurations are optimized for charcoal over coal (as well as for anthracite coal vs. bituminous).

[ThomasPowers]

Charcoal and coal have similar BTU's per pound; but their densities vary quite a bit!   First heat also depends on the starting temp of the metal which in Minnesota could be rather *brisk* this time of year.

[Deep Forest Tinker]

Thomas, that's a very fair point, I was starting from 31F since the stock was sitting in my garage.

I'm going to try burying the rod in the charcoal. I'll try coal at some point, but my forge is based on a charcoal design and I want to stick with that for the immediate project. 

[SReynolds]

For the love of Pete , would somebody please post up the picture from this site of what a firelooks like with a steel rod in it. I have it. But it is AWOL

[Frosty]

55 minutes ago, SReynolds said:

For the love of Pete , would somebody please post up the picture from this site of what a firelooks like with a steel rod in it. I have it. But it is AWOL

Who is this Pete guy Mr. Reynolds? A lot of affectionate people solicit favors for him but I've never known why. Would you mind introducing us please? I bet he's a wonderful person to know.

Frosty The Lucky.

[SReynolds]

He is a great guy! LOADS of folks love him.

[Deep Forest Tinker]

Yeah, I've seen that one before but I wasn't sure if it applies for charcoal. I wish I could find a diagram of how a charcoal fire is supposed to be built and where the workpiece goes. My forge is quite a bit like this (but i built it for $70) 

Anybody know how deep I should have the fuel? i usually have about 4 inches with my workpiece laying on top. now i'll try to make it more of a mound with 4 inches under and maybe 2 over and see how that goes.

Other newb questions if anyone's willing to keep humoring me:
1) say I want to flatten a rod of 5/8" thats a foot long down to about 1/4" bar. how many heatings should that take? it takes me a LOT so i dont know if thats normal or my technique sucks

2) i guess lots of heatings is bad for the metal, so how many times can something realistically be heated before it's a problem. all I've heard is "too many" is bad, but i have no reference for what's normal or a lot of heatings. any guideline anybody can give me?

So do you have to brush all the stuff that gets stuck to it off every time you hammer it?

Also

[Glenn]

Fuel (solid fuel) does not make the fire hot, air makes the fire hot. Fuel is a consumable item. You use as much fuel as is needed to get the heat you want, or need. If there is a question, add more fuel. The cost of the fuel is small compared to your time and frustration.

 

 

[Buzzkill]

1 hour ago, Deep Forest Tinker said:

1) say I want to flatten a rod of 5/8" thats a foot long down to about 1/4" bar. how many heatings should that take? it takes me a LOT so i dont know if thats normal or my technique sucks

This is one of those questions that sounds really specific, but there are so many variables to take into account that it's hard to give it an accurate answer.  What steel are we talking about?  High carbon or stainless tend to not move as well under the hammer as mild steel and can have significantly different forging temperatures.

What hammer are you using?  An 8 oz. ball pein hammer is generally going to take longer than a 3 lb. drilling hammer.

How is your hammer control?  Are you able to consistently hit where you want to hit on the rod?

What temperature (color) are you forging at?  Most steels are going to move significantly different at a yellow heat compared to a dull red.

All of these things (and possibly a few others) can impact how many heats it takes to get the steel into the shape you want it. 

If at all possible for you I'd recommend getting involved with a person or organization that can help you.  This is where you can learn more in an afternoon with someone else than you can in several weeks of trial and error on your own.  Both ways work.  One is just a whole lot faster and a lot less frustration.

[ThomasPowers]

To flatten: 1 heat using your powerhammer correctly.  (what alloy, what hammer how fast you hammer, do you need to dress the sides are is just flattening ok?  I'd say at least 2 using a 1500 gm hammer and working mild steel at high heat and not needing to dress the sides.)

At some point the metal will scale away to nothing but scale and that would be the endpoint.  Now mild steel can be heated and reworked pretty much,  forever the forging dealing with possible grain growth and not having to worry about decarburization.  High carbon steels are different as decarburization is a big issue depending on what you are trying to do with them and grain growth can start being a factor at high heats and light forging depending on WHAT YOU ARE TRYING TO DO WITH IT.   (My car has a 1/4 tank of gas; can I drive home with it?)

[SReynolds]

no......you will have LESS gasoline by time you reach home.

Why can you not photograph an Indian with his hat?

[Deep Forest Tinker]

1 hour ago, Buzzkill said:

This is one of those questions that sounds really specific, but there are so many variables to take into account that it's hard to give it an accurate answer.  What steel are we talking about?  High carbon or stainless tend to not move as well under the hammer as mild steel and can have significantly different forging temperatures.

What hammer are you using?  An 8 oz. ball pein hammer is generally going to take longer than a 3 lb. drilling hammer.

How is your hammer control?  Are you able to consistently hit where you want to hit on the rod?

What temperature (color) are you forging at?  Most steels are going to move significantly different at a yellow heat compared to a dull red.

All of these things (and possibly a few others) can impact how many heats it takes to get the steel into the shape you want it. 

If at all possible for you I'd recommend getting involved with a person or organization that can help you.  This is where you can learn more in an afternoon with someone else than you can in several weeks of trial and error on your own.  Both ways work.  One is just a whole lot faster and a lot less frustration.

Yeah, i'm just trying to get a bead on what should be reasonable if it is being done right. So the color of the temperature doesnt matter since I'm only looking for how long when it's being done correctly i.e. yellow hot. 

That said, the other factors are O1 steel, and a 3lb hammer. 
 

I should get involved with an organization, I just don't have much access. I think there's a guild within 30 miles, even one day of watching soemone more experienced work would probably teach me more than i know now. 

[ThomasPowers]

Yellow hot is too hot for O1  JPH suggests 1800-1950 deg F as the start forging temp in the complete bladesmith and a quick search on heat colors for blacksmiths will give a chart.

[Buzzkill]

As Thomas said yellow heat is too much for O1.  It may fall apart or "cottage cheese" on you there.  Orange is better.  It's not super hard to work with, but I wouldn't call it beginner steel. It certainly doesn't move as well under the hammer as mild steel and has a less forgiving forging range. I destroyed a few pieces of O1 in a coal forge before I decided propane was my better option, but I'm nowhere near an expert smith or an expert with coal. At my level I'm guessing around 5 or 6 heats to get a foot of 5/8" O1 drill rod down to about 1/4" thick, reasonably straight and flat.  O1 has a couple other "quirks."  It will air harden some in thin pieces, and if you try to forge it cooler than recommended there is a very high chance of cracking it.  I've cracked a couple pieces just "tweaking" them a little at a low red.  That wasn't even forging or really moving the metal, just bending.  They were small/thin pieces though.  Also make sure you take a good look at the heat treatment specifications given by the manufacturer.  It's not a super complicated steel to treat, but it's not the same as a simple steel either.

[SReynolds]

http://www.azom.com/article.aspx?ArticleID=6229

 

[Deep Forest Tinker]

wow, thanks for the advice. I'll keep trying wtih my O1 stock but what's an 'easier' steel? I have a Grainger supply 1/2 mile from my work so I can get a few options pretty easily. 

[Latticino]

Depends on what you are planning on making with it.  As others said, if you don't need high carbon to harden for tools or knives or the like, you should probably try to use low carbon steel (10 series is good – say, 1030 or below; A36 in a pinch).  If you do need high carbon steel 1070, 1080, 1084, and 5160 are all pretty forgiving.  You can usually source 5160 from automotive spring shops (their cutoffs for replacement springs) for free or a box of doughnuts.

[Buzzkill]

5160 is pretty forgiving in forging and heat treat, and the 10xx series are good for blades where the xx's are in the 70's to 90's.  If you're making hammers you probably want to look at something like 4140.  Specific steel choice will depend on what you want to make and what characteristics you want it to have.  In general, the higher the carbon content the harder the steel after quenching, but that also means its more subject to breaking or cracking rather than bending.   If you want it to flex more before breaking then lower carbon content and higher temper temperatures after hardening are what you are after, but for a blade that would mean less edge retention.  It's a balancing act of sorts, but with information and experience you can put the balance point between tough and hard where you want it.

[ThomasPowers]

Steel hardness after quenching maxes out after a while and then the extra carbon can help with edge retention by going into various carbides...