Our group just got our new forge and I have done my first few blades this last two days. One thing I get is small cracks in the blade. Why is this? Has it to do with temprature or with the steel I use? While learning where to hit with the hammer I have used old steel bars and old nails I have in the celler of my old mill. Is it the qualtiy of this steel that makes the cracks or could it be the coal I burn. Anyone have some experience to share?

I will put out a few pictures of my seaxes soon!

Hej Martin,

It can be that you both overheat (causing large grain) and then cold working causing stress and fracture.

Start forging from a good lemon yellow and stop forging at tomato red. That should keep you on the safe side.

Never trust these colours completely as they will depend on lighting in the smithy. If you are forging out doors they will look much cooler, if the room is very dark they will look lighter.
It is just a general guide.


Good luck!

its not much of an issue with simpler steels, but with some alloys you must preheat the steel to a temp in the range of about 900F to 1100F, and then allow temp. to equalize before heating the billet up to forging temps. Some alloys can crack unless they are allowed to adjust to the heat. before getting to full heat, because the expansion of the metal causes extreme stress. Others like L-6 dont like to be hit below 1550 F. others will short at too high a heat, read the mill spec's of your steels, most have warnings about preheating and red short problems, where they apply.

Isn't oxidation also one of the major causes for cracking? I find that heavy oxidation goes hand in hand with cracks forming in the spine of a blade, when working with low carbon steel. In particular when the blade bends back and forwards a lot, scale becomes traped in the iron forming vertical bands, which are the start of cracks that start at the spine of the blade. Usually if these occur, they don't go deeper then 1-2mm into the blade, but they are quite annoying. This heavy oxidation usually happens because I spend a lot of time talking to the public at the living history center, so the blade spends much more time then needed in te fire. But if I work more quickly, there's much less oxidation, and no cracking.

I think that chapter 2 of the Compete Bladesmith should help a lot when forging known steels, since in it they are given forging temperature ranges for the most diffused steel in the US.

For us european smiths or smith wannabe things are a bit more complicated but I guess that universities and firm producing steels should be helpful at spreading informations about the composition and working temperature range of Europe made steels .

Also Hrisoulas gives the composition of each steel he describes, so a comparison with our steels could be easily made.

Hi Martin

Did you get the cracks simply after forging, or have you HTed them ?

Fab

I had a similar problem when I started forging. As has been said, some steels don't like to be worked in certain temp. ranges, others are more forgiving. 5160 or 10-series are good to start with.
Another problem I had was corners folding over when forging on the edges and causing cold shuts in the surface. These look like cracks and will usually form along the edges of the piece, running lengthwise, they are usually shallow but very annoying.

Here is a picture of one of the cracks and also a picture of the whole seax so far...

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My brother and I built a seax together last month and experienced the same issue. He used 4140 for the blade, and didn't notice the cracks until after heat treating. He attributed the cracking to working the steel outside it's prime temperature range for forging.

It was his first attempt at making a blade, so he was pretty bummed out about the cracks. He tried grinding them down, but they run too deep. Normalizing doesn't get them hot enough. I believe he also tried reheating one secion to melting in hopes that enought steel would melt and pool to close up the cracks; this led to new cracks in a ripple pattern.

In any event it appears (to two rank ametuers) that once the cracks are there, you're largely stuck with them, short of reforging. in the case of the seax, he feels that they are not a significant threat to blade integrity, and the end product was destined to be rough anyway so we just accepted it. Next time he's going for the simpler steel. ;)

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Those look like the cold shuts I described above, if you did any forging on-edge to thicken the spine or maintain the width as you drew the taper this may be what happened.

Martin,

I had the same problem when forming the tang of my Seax. Luckily they weren't too deep though and the tang had ended up thicker than I had intended, so to be honest, I just ground them out.

[quote=\"Jeroen Zuiderwijk\"][quote=\"Martin Wallgren\"]Here is a picture of one of the cracks and also a picture of the whole seax so far...

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You mean the lengthwise \"crack\"? That\'s the kind of fold Justin described, when the steel overlaps itself. If it were real cracks, they\'d go across the spine, rather then along with it. The folding most frequently occurs when you for a tip, but there are forging techniques to prevent this (depending on what you start with).

Regarding the book \"Compete Bladesmith\", I find it highly overrated. I\'ve read it before I started forging, but I didn\'t learn anything from it, aside from the forging properties of some more exotic steels. The information in it is far too basic, and most you can figure out by yourself. The real trick is in all the nuances to make the techniques work. I personally find that I learn a lot more by looking at an experienced smith at work, and simply asking questions. And showing problems by posting photos and discussing them like in this example is definately recommended, if you don\'t know a smith you can ask questions that is.[/quote]

Well, surely the enthusiasm of the reviewers at Amazon is quite a bit of hype, however Martin won\'t easily find too many people around him that will teach him, as long as he is not living close to some serious smith wishing to partake his knowledge.

Instead than looking at online forums one can have all the needed basics in a easily portable format.

I have also found online a pdf book that explain basic forging to african blacksmith, it has a lot of tips to recycle old car parts int basic instruments.

I don\'t know if I can repost it here or elsewhere, however, since I have lost the link to the original page.

Thanx all for your kind help!

To morrow I gonna have a session in the forge and we will take pictures and I´ll tell you how it went. Also the morning will be a session with the file on the seaxblade I did friday night. Will show pics of that too.