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Mild steel cracking


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Hi, yesterday I began to forge a new pair of tongs. I started with 3/8" x 1" mils steel and I fullered it with my flypress. When I was drawing the handle, I noticed there was a lot of cracks on it. I never forged it colder than orange color, it was always yellow and I stopped when orange. One rein was correct but the other was definitely ruined by these cracks. What happened? My dies for the flypress is 2 pieces of 3/4 round that act as a fuller so there is no cold shuts...

 

The first pic is the 2 reins when I stopped working on them because of the cracks. The second is the one that is fine and the others ares the cracks in detail of the other tong.

What can cause that? I'm pretty sure it is not the flypress because it is not powerfull enough to squeeze the metal in one heat, it took several. Is it the repetive heats?

I must tell that I'm using hard anthracite (clean one) as a fuel. I wonder if it can transfer carbon to the steel due to repetitive heats and then becoming brittle?

I noticed that when I put a little piece in the fire several times, it tends to develop cracks too, that's why I'm asking for the fuel... And it never happened with coke or coal.

 

For now I will have to forge weld a piece for the reins because the cracks are too deep it will shatter when put into stress I guess...

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Yes Macbruce, I learned that last week :wacko: when I quenched a 1/8 thick plate in water and then bend it cold to a 90 degrees angle... It snapped at 20 degrees and the center looked like carbon steel... By chance I didn't receive the piece on my face.

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There is something to be said about the light in your shop.  The old blacksmith's have minimal light which may give a truer color for the naked eye.  I have learned to turn out the lights in my shop, during the day, and close the doors, if I need to be sensitive to the color changes in the metal I'm working.  I really noticed this when working with bronze.  I know there are lots of different types of light bulbs made today and they will change how you see colors.   

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There is something to be said about the light in your shop.  The old blacksmith's have minimal light which may give a truer color for the naked eye.  I have learned to turn out the lights in my shop, during the day, and close the doors, if I need to be sensitive to the color changes in the metal I'm working.  I really noticed this when working with bronze.  I know there are lots of different types of light bulbs made today and they will change how you see colors.

Lamps ( light bulbs) are rated with a CRI color rendering index, this higher the number the better the color rendition. Also they carry a kelvin temp for the color of light output. The higher that is the closer to true sunlight. So a fluorescent lamp in a house might be 3500
K and 70 CRI. In my shop I prefer 4100k and 80+ CRI. But I still like it dim so I can see the color of the light from the metal.
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What about grinding down to good metal before deciding to start over?  I forged a gardening tool this weekend and burned it slightly.  Cooled it, then ground it down to what looks like good steel, normalized and then finished the cultivator.  As I'm uncertain about it's integrity though I'm keeping this one for myself vs. selling it.

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The steel is 44W (A36 for US I think?). Is there any issue with working it at yellow color? This is the only mild steel they sell at my local supplier and I'm a total newbie with the differences in mild steels.

It think it may be because of my new light bulb (fluo compact) I must have misread the color of the steel.

If I grind it to remove enough of the cracks it will be too thin, so I'll cut the bad part and weld a new rein (the jaw is still in good state)

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If you're using something like A36, it could be anything and not necessarily mild steel.  

A36 is a structural grade which means it need to meet certain criteria for strength not for composition so it may have alloying elements that make it air hardening or hot short or just completely unsuitable for forging. 

And that may just be a 6 inch section in 5 foot worth of bar  or it may be most of a bar.  

Since there is a lot of recycle in structural grades they become a crap shoot, sometimes you get a lovely to forge piece, sometimes you get a section that falls apart no matter what you do.

 

ron

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If you're using something like A36, it could be anything and not necessarily mild steel.  

A36 is a structural grade which means it need to meet certain criteria for strength not for composition so it may have alloying elements that make it air hardening or hot short or just completely unsuitable for forging. 

And that may just be a 6 inch section in 5 foot worth of bar  or it may be most of a bar.  

Since there is a lot of recycle in structural grades they become a crap shoot, sometimes you get a lovely to forge piece, sometimes you get a section that falls apart no matter what you do.

 

ron

Thanks for the explanation on A36, I didn't know that this steel can be different in composition from batch to another batch.

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take a look at how deep your fire, with your metal in the orange or yellow range. Your working area of forge  Coal is like a ball  the bottom of the ball will oxidize the metal the top will pick up the junk where your coal is  converting to coke. I have seen this happened in rivet forges where the fire pot is not deep and the depth can be fixed with a few bricks to make the mound of coal deeper and bigger.

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