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4140 Cracked when hardening

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I have been anvil hunting with little luck, so I decided to stop by my local scrapyard today. I came home with a couple chunks of 4140 that are 3"x2.5"x10". I would like to harden one's face and sink it in some concrete for a post anvil. Any suggestions on trying to harden it? I don't know how much I should try to harden, like just a few inches, or what? I have a small forge I can heat it in, or I could use my HF weedburner and give that a shot. I don't have anything but old motor oil on hand to quench with at the moment, but I could get some better oil if need be. I was thinking about a 400° temper after hardening. 

 

Any thoughts or wisdom to share?  I could bang on it as is, but I would rather it be a bit harder first as it is pretty square and flat at the moment. I am planning to dress the edges a bit before the ht.

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Happy New Year,

 

Anvils work harden. Go to work on it, Don't hit the anvil directly, hit the Hot-Spot. It's magic, it takes quite awhile, but between now and then you will learn to respect the anvil face!!

 

Neil

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Typically anvils do not require tempering as getting overhard on such large chunks of steel is unlikely.  Anvil hardening is usually done with a water drench tank that is dumped onto the anvil rather quickly.  You'd have to make a special fire designed for the purpose... it seems a bit much to tackle at the stage where you are.  I'd say that you'd be wise to use it as is for now.  4140 is pretty decent steel and will wear pretty toughly even in an unhardened state.  Your plan to mount it in cement is a good one.

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i don't think you will get that chunk of steel to critical temp with a weed burner.  Use it as is.

what orientation were you going to place them in?

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I do have a propane tank converted to a forge that I can fit these pieces in. They are big chunks though, weighing around 15 lbs each. I was thinking of just using one set up on end for now and getting all the mass under the hammer.

 

I was also debating on refacing my HF ASO with one of them. I was reading up last night on welding cast iron to tool steel. 

 

They have a few more chunks there and its  .85¢ a lbs for those. I was thinking about getting a big hunk of a36 or something like that and facing that with some of these 4140 chunks. Many ideas in my head. I could weld several of the 4140 chunks together ...

 

I also have a 4ft section of light train rail that I could throw into the mix. What if I cut the section of rail and welded a 4140 chunk to it, turned on end, and make a larger post anvil? I could embed that in a concrete base.

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A peripheral arc weld won't cut it, you need 100% surface bonding, which means getting both chunks up to a nearly white 'sweating' heat in a monster forge, and perform a full contact forge weld: hammering them together in a huge power hammer, then quenching the face under a waterfall. Which is why no one does that anymore.

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Typically anvils do not require tempering as getting overhard on such large chunks of steel is unlikely.

 

I do not agree.  Any hardening process requires some tempering to relieve the stess built up from the quench.  It is not a good idea to harden then leave it brittle,  that is asking for trouble.  Tempering does reduce hardening a bit, but if you read the Heat Treat post in the knife section that I spent many hours writing, it explaines temperings purpose is to relieve stress.

 

I think 4140 will work harden just fine for a usable anvil.  Also HT of this will be more effort and annoyance than you need since 4140 is barely hardenable anyway.

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I agree with steve.  Use as is on end.  Just make sure you have it solidly mounted.  Do hot work on it then it is completely fine as is better than going through all the effort.  Use your ASO for cold work.  I do a lot of chisel pearsing and have a chunk of a36 for it.  Thats the stuff you want to stay away from on that anvil.  Make a cutting plate for hot chisel work as you can dent the surface easily if you don't protect it from the chisel.  

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I would not use water on 4140.  That may seem like a big chunk, but you can still crack it by cooling too quickly.  I build my power hammer dies out of 4140.  I quenched them in slow commercial quench oil.  One of them cracked when I took it out of the oil after five minutes and cooled it the rest of the way with water.

 

Tempering will not hurt anything.  Cheap insurance.  For an anvil, I'd do between 535 and 600, if you can. 

 

Or you can try them as-is and see how they do.  They may already be heat treated.

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If I remember correctly, there is a problem with tempering 4140 to 500 degrees +/-.  There is NO NEED to HEAT TREAT 4140 for your application. Seems to me this has been said over and over!!

I guess I am just a Grumpy Old Man, quit worrying about your 4140 and work it!!

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What problem?  I tempered my power hammer dies at 600 degrees and axes and tomahawks at 535 with no issues whatsoever.  That's the first I've heard of anyone thinking there's a problem tempering at that range.

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Ah the infamous "blue brittle" effect!

 

85 cents a pound is high; look for broken forklift tines and try for 20 cents a pound!  Be sure to explain what you want them for sometimes forklift places will give you one IFF they *know* it won't be reused on a forklift.

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Did a Google search on "blue brittleness" and did a bit of reading.  Interesting, but not a phenomenon I've personally seen in 4140.  Like I said, I temper 4140 for the applications I need in the 535 to 600 degree Fahrenheit range, and have used the resulting tools extensively and hard without anything but satisfaction in the result.

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Happy New Year Stormcrow,

 

Look up in your Heat Treating Book. If you don't have one, you should.

Sometimes, you bite the dog. Sometimes, the dog bites you. :) :)

 

Neil

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Ok guys, I know everyone says just use the piece, so I will. The thing is, I have like 4 pieces of it that are all equal size. So I decided to play around with one of the chunks tonight.  I heated it in my forge for a couple hours.  It was around an orange color and holding there, I don't think I could get it much hotter in my small forge, so I finally quenched one end in used motor oil.  It kept trying to set me on fire and it was a big chunk to hang onto with my tongs. I need to replace my home depot bucket with a metal one, I didn't wanna burn through the bottom.  :)  So after about half of it got quenched, I ran down to the canal in my back yard and plunged it in for the finale.  I ran it in my toaster oven for about two hours at 400-F after that.  I figured it couldn't hurt to see what happens. If it doesn't work, then oh well. I didn't hear any pinging when it quenched.  It was a fun experiment, no matter what happens.

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When quenching 4140 hammer heads in 130F warm oil, I always have to vigorously agitate to get it to harden. Just holding it there usually doesn't harden for me. I imagine in a more extreme way your route considering the size.

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I took a 1" ball bearing out this morning and tested the hardened piece. On the end that was not hardened as well, I get about 35% rebound. On the end that I hardened, I am getting about 75 - 80% rebound and a nice ring out of it. 

 

My 8 year old son has had a lot of fun "helping" me with this project so far. He was amazed by the quench and had a lot of fun with our rebound testing this morning. I have to keep an eye out and make sure that my 1" ball bearing doesn't "disappear" now. :)

 

I asked this question in my other thread on homemade anvil plans, but no one has answered it. Should I weld this hardened piece to another piece of the same, or weld it to like 24" of light rail on end, to make a post anvil? I know I could just sink it into concrete, but would it be worth the extra effort to add some mass to it first? 

 

Thanks for all the help.

 

 

Do not repost the same thing all over the forum, that will only upset the natives.   Just wait and it will get answered.  I am sory if 11 hours is too long for you to wait for an answer. 

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I would just sink it in some concrete or even just sand.  I think you should temper it a little more than you have already.  You don't want a corner breaking off and potentially hurting someone.  If a sharp file will just cut the corners you should be ok but if not I would heat it to at least 600 degrees.

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The sound is detrimental.  Wear ear plugs.  Deaden the sound with magnets or use silicone.  I have a wonderful anvil that doesn't ring (I still wear ear plugs) and it has a 80 to 90 percent return.  I just cringe every time someone mentions the ringing in a positive connotation.  The ringing is only good when your trying to get a dinner bell or a bell out of the piece.  I would recommend mounting it in such a way as to deaden the sound and still make sure that whenever your in your "shop space" especially with the impressionable youth that everyone wears every piece of ppe regardless of if there is any work being done.  Good habits are hard to form but bad habits can cost someone their life.  

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I quenched them in slow commercial quench oil.  One of them cracked when I took it out of the oil after five minutes and cooled it the rest of the way with water.

 

You did it backwards... use the faster quenchant until material is just above Ms, then use the slower one.

 

So after about half of it got quenched, I ran down to the canal in my back yard and plunged it in for the finale. 

 

You did it backwards... use the faster quenchant until material is just above Ms, then use the slower one.

 

Look up in your Heat Treating Book. If you don't have one, you should.

 

Neil gets it. "The truth is out there..."

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Thingmaker3 - I should have just been patient and left it in the oil.  The other did fine, as did the one I built to replace the cracked one.  4140 is good stuff, but it doesn't need rushed.

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Does one of those pieces match the ASO's face? I've been wanting to try facing an ASO with good steel but haven't gotten around to it. My plan was to grind the ASO to match the steel as closely as possible. As in smoking and rubbing the two together till the soot rubs off completely. Then silver solder them together.

 

Sure it'll take a goodly fire and some time to soak the ASO to brazing heat but a little flux and good solder aught to do the trick.

 

will it be tough enough you ask? I doubt very any human is strong enough to do anything to that size braze. I can't count how many carbides I silver soldered to drill teeth and then sent down the hole to grind on frozen gravel. The carbides never once separated from the teeth, teeth broke and wore to nubs but the soldered joints never failed.

 

Of course that's a thought I haven't tried but can't think of a reason it wouldn't work.

 

Frosty The Lucky.

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Hey guys I have a question on 4140. I forged a small hammer out of new 1 1/12 hot rolled 4140 round stock. I then heated it to non magnetic and let it cool to room temperature to normalize it. I then took it back to non magnetic and quenched it in warm vegetable oil I didn't check the temperature for sure it was nice and warm to the touch. When I polished the ends right after quenching to temper it it had cracked. What did I do wrong? I've done some reading on 4140 and can't find anything that stands out that I really did wrong unless I should have annealed it first. Can you guys tell me what I messed up? Thanks

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Where did it crack?  Sharp corners and cold shuts can cause stress risers.  Pics would be helpful...

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Vegetable oil is actually a faster quench than normal mineral oil.  I am not sure if 4140's correct Austenitizing temperature?  The Nickel content may throw it off.   Quenching from too high a temperature can cause cracking

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