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cracked spear


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So, there I was trying to forge a basic spear from a 3/4 coil spring. After roughly forging the socket, I went to town on the spear blade. As you can see from the rather dark picture, two cracks propogated across the socket. The one that concerns me the most is where the socket meets the blade. I know this is a silly question, but if this is caused by putting too much stress on it while forging, how am I to avoid this in the future?

Mark

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Cracks such as the one at the "waist" are sometimes termed "brashness".They can be caused by a number of issues:

*The spring being used,it(the flaw)could've already been there

*Improper thermo-cycling:Worked too hot,without enough normalising cycles,oran initial anneal,causing the enlargement of the grain,thus weakening the intragranular connections.Or,worked too cold,causing a partial work-hardening,and thus stressed to breaking.

*Harmonics.Basically a type of work-hardened damage caused by the parts bouncing around while forging one or the other.

*Nimber of combinations of some/all of the above...

One major change of a plan that i can think of would be to leave the fullering to the very last.
And,if one absolutely must use this steel for the job,to try working it very hot(yellow),with frequent normalising heats.Holding something like this,bar-bell shaped weight-wise,is best by placing the tongs as close to the weak spot as practicable.

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So, there I was trying to forge a basic spear from a 3/4 coil spring. After roughly forging the socket, I went to town on the spear blade. As you can see from the rather dark picture, two cracks propogated across the socket. The one that concerns me the most is where the socket meets the blade. I know this is a silly question, but if this is caused by putting too much stress on it while forging, how am I to avoid this in the future?

Mark


While teaching in my school I observe quite often the situation when students bring to heat quite a long portion of a workpiece say 5 “ while actually hammering only half of it at best. This causes grain growth and after several heats it falls apart without even applying any hammer hit. This especially true in case of alloy steels ( Cr, Va, Si) which some coil springs can comprise. Conclusion: if you brought a thing to heat do something to it – it’s like making love, sorry for the comparison. Also another prove that spot heat is best (viva char coal forge!)

In my opinion coil spring is not the best material option for a spear. Ideally, it should be iron with steel welded or carbonized edges. Steel is always difficult to forge (meant shaping with hammer) and ancient blacksmiths always tended to avoid as much as possible. It is not they were short of steel (they were short of both steel and iron). They simply fell into most efficient input-output balance, like every sustainable natural system does with time.
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*Improper thermo-cycling:Worked too hot,without enough normalising cycles,oran initial anneal,causing the enlargement of the grain,thus weakening the intragranular connections.Or,worked too cold,causing a partial work-hardening,and thus stressed to breaking.

O.k., newbie question.
Help me with the term "normalizising cycles" what is it and how do you do it?
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I have the same problem with a half-integral knife I forged out of c105. At the transition between tang and bolster I have many of these small fissures and cracks.

I ask myself if this can be "repaired" by bringing it up to welding heat (with flux) and weld these fractures together again.

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Pay attention to Jake and dancho's commentary here. I have experienced failure in each point they have mentioned at one time or another.

Also, did you use some sort of fuller to neck it between the point and socket? I have done great violence to pieces with a spring fuller in days gone by. Particularly from rotating the piece in the same direction and working at too low a heat. This will actually twist the fullered section.

A simple normalizing cycle will look like this:
#1 heat to critical, hold in still air until it cools to black.
#2 heat to almost critical (a little lower than the first heat), hold in still air until it cools to black.
#3 heat to almost, almost critical (a little lower than the second heat), hold in still air until it cools to black.

You oughta get in the habit of doing this often when you're really pushing a piece of carbon steel. It relieves the stress we introduce by forging. Think of it as spa therapy for the steel.

I ask myself if this can be "repaired" by bringing it up to welding heat (with flux) and weld these fractures together again.


Probably not. Especially if you have already over-heated it. You're welcome to try, but a cracked piece usually ends up in the scrap pile.

Hope this helps.

Don
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Well the tendency to make cutting tools of iron and then steel the edge was often an economic one; even as late as the American Civil War good steel could be 5 times as expensive as iron so why pay for it where it wasn't needed?

Having made steel from wrought iron using the blister method the time and fuel costs do add quite a lot to the cost of the material.

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Thanks for the wealth of information folks. It really helps me to understand a number of areas that probably went wrong. I used the coil spring to see what I could do with it. I had success making chisels and punches with it and thought I'd give it a go. It clearly turned out less than stellar heheh.

Could I get a little more insight into why heating it without working it is bad, but normalizing it is good? If I understand correctly, forging it after heating prevents the grain from growing uncontrolled, but isn't normalizing heating it without working it? Is it a case of a little being good but long term repeated heating without working being bad? Because I can certainly see that portion getting heated frequently without being worked due to it's proximity to the blade.

Dancho, you mention iron as the best material with steel forge welded to it. Is mild steel an acceptable altenative as iron seems a bit hard to come by?

Don A, I fullered it on the edge of the anvil, as I've yet to make any fullering tools.

Jake, there is no requirement that I use this steel. What would you recommend?

Thanks again for all the useful information folks.

Mark

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Hi,Mark.
The "best" material for anything is something that you've grown comfortable with.Forging it,heat-treating,all of it.

Mild is definitely an alternative to WI,even better in many respects(consistency,for one).

Use mild,if you're comfortable with welding,subsequently,or cementation.Both are great things to learn and to practice.If not,then most 10xx steel would probably be easier to get good with,and preferrably new material.

The difference between the heating and normalising is the temp.The grain enlargement happens above critical,and forging heat is usually WAY above that.Normalising only takes it to,and the 2-nd and 3-rd times,below critical.

Best of luck.Jake

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Could I get a little more insight into why heating it without working it is bad, but normalizing it is good? If I understand correctly, forging it after heating prevents the grain from growing uncontrolled, but isn't normalizing heating it without working it? Is it a case of a little being good but long term repeated heating without working being bad? Because I can certainly see that portion getting heated frequently without being worked due to it's proximity to the blade.

Dancho, you mention iron as the best material with steel forge welded to it. Is mild steel an acceptable altenative as iron seems a bit hard to come by?



I'd say simplyt try to heat only that part you are going to forge and in my experince this is best achieved in a side blast clay forge run on char coal . If you can't provide the condition then you need normalizing heat treatment to make the grain smaller.

As for the steeling the edges -- well, I would call iron in this case anything which doesn't take hardening and easier to forge into some shape like socket. Obvouisly, the tasks for the socket and edge are completely opposite. Good edge is at least 0.8 % C. For the edge you need as liittle as 5 mm wide strip of 0.8-1 % C steel. It is quite logic to add it to the main body made of something else. Or carbonize the completely ready object like I do with my axes, spears, knives and other tools. It works. Try mild steel first and play with it, make all you want to do what hard steel never will allow you. Just go with the flow of metal and see where it brings you and than once you understood the game put some carbon spots anywhere you like.
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Well the tendency to make cutting tools of iron and then steel the edge was often an economic one; even as late as the American Civil War good steel could be 5 times as expensive as iron so why pay for it where it wasn't needed?

Having made steel from wrought iron using the blister method the time and fuel costs do add quite a lot to the cost of the material.


Hi Thomas!

Yes, for the times and metallyrgy production methods you've mentioned I completely agree.

However, there were lots of experiments (I personally took part in some of them) which clearly show that in an ancient low furnace for direct reducing iron sponge from ore ( like russian ones of 10 AD) you can easyly with not much extra effort and fuel obtain steel sponge instead of iron one. The next stages are absolutely identical for both. This mean you don't need iron to produce steel, you can go direct, like in modern process.

But I am talking about other things.

Iron is much easier to forge than high carbon steel which gives the edge. This is eqally true for 10 AD as well as for 19 AD or 21 AD. Not only the effort to cause deformation but also:

* your forging range is much more narrow

* always a danger to desrtoy the object completely
* because it's harder you need more heats to get to the same result which means
more lost in scale (up to 60 %)

In case of ancient ruusian axe which is the subject of other topic in the forum I would NEVER go to make it of anything else but iron or at least mild steel. You simply will not get the shapes you want with steel more that 0.5 %C.


and still this not enough for the edge I like (with 1.2 %C). I think that's the case when compromises do not pay and we better separate thing from each other. Black from white. Steel from iron.

Bogdan
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My experience (about 10 years serving on a smelting crew) is more with Scandinavian short stack bloomeries of the early middle ages and yes a high C bloom is a possibility just like with the Japanese Tatara furnace.

This does beg the question on why they went to a fuel intensive blister steel process instead of just running an adjunct bloomery to produce High C material. My thoughts were that perhaps a better more uniform material was producible even with having to test each rod from the chest for sap *and* the best iron for steeling was oregrounds from Sweden and easier to import WI than ore (and cheaper than steel!)

With your experiences do you have any ideas on this too?

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Probably not. Especially if you have already over-heated it. You're welcome to try, but a cracked piece usually ends up in the scrap pile.

Hope this helps.

Don


I think the cracks developed due to stresses at that location when it was too cold. I worked the blade itself while putting stress on this transgression between bolster and tang, and that area due to being much thinner cooled down quick.
If it doesnÄt work I'll cut off the tang and forge down the bolster to recycle the forged blade material, it won't be an integral anymore, but at least the work wasn't for the trash bin that way.
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This does beg the question on why they went to a fuel intensive blister steel process instead of just running an adjunct bloomery to produce High C material. My thoughts were that perhaps a better more uniform material was producible even with having to test each rod from the chest for sap *and* the best iron for steeling was oregrounds from Sweden and easier to import WI than ore (and cheaper than steel!)

With your experiences do you have any ideas on this too?


I am not a specialist in these questions concerning metallurgy, but it seems to me it refers more to centralized power, world trade, wars, politics and such -- not really quality of metal and art of smithing. What I heard from others is that inspite of the fact that wrought iron is produced from cast iron (extra stage compared to bloom process) it is more efficient for bigger scale production. One of the reasons is high level of personal knowledge needed to run bloomery process properly .With cast iron you can involve masses of less trained work force.

However I am completely sure about the fact that a thousand years ago bloomeries produced material of at least not worse quality than wrought iron and blister steel. Returning to my axes -- they need very high quality of iron, higher than 18 ct AD regular welded eye axe need. Any weak spot and they will split at one stage or another.. I often have to pre –weld modern mild steel to prevent this.
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