4140 Cracked when hardening

[JNewman]

 

From my experience, as a shop that uses 4130 by the ton every single year, as much as I was told that 41xx was oil hardening, I've never gotten better results than with water hardening. We do several hundred theatrical combat swords a year ranging from 3/16th down to 1/8th and have been quenching in warm water for the past 4 years with awesome results. These are pieces that get used and abused by actors in stunt shows, we offer a lifetime warranty, and we get back maybe 2 or 3 pieces a year that have broken, most of them older pieces from when we used to send them off for ht, or a rare brittle weld at the crossguard or pommel. That being said, I've done 2 - 4 lb hammers out of 4140 the same way with equal results, but for a block that size, I'd make sure I had a lot of water!

J

​I won't argue with your results and it is a big chunk so may need water to get hard enough.  But the OP is a beginner and does not have temperature controlled furnaces and may get the steel too hot for the quench or an uneven heat which might crack it.  If he ends up soft it is not a tragedy, a crack would be for him.  I have had 4150 crack after an oil quench. 

If he can send it out for HT for a reasonable price that would be a good option as heavier sections are supposed to be held at temperature for a couple of hours anyways. 

I just looked up 4130 in my copy of the ASM Heat Treaters Guide and even thought the procedure is to quench in oil most of the graphs are based on the steel being quenched in water.  The same charts in 4140 are based on being quenched in oil.

I have some coke oven chisels that I forge out of W1 which is a "water hardening steel" but if I quench them in warm water I get 3-4 out of a batch of 50 cracking.  If I quench them in oil I get them full hard to the core and no cracking. 

Edited February 25, 2015 by JNewman

[gearhartironwerks]

Imho, 4140 is really no good for blacksmithing work. The dies on my Saymak are 4140 and are basically worthless. I have surface ground them and heat treated several times using both oil (waste of time) and water. The water works best with no tempering. They cannot standup to daily use and form saddles. This, after ht in a temp controlled oven.

Before Grant Sarver died, I had a long discussion with him about 4140 ht. He suggested going by the book using oil for a quench, but finally admitted that water was best for everything but small sections.

John

Gearhart Ironwerks

 

[ThomasPowers]

Are you sure they are really 4140?   A lot of folks have had their steel supplier goof up and send the wrong stuff before.  Why big companies tend to test inputs on a regular basis.

[Dahlia's Daddy]

I would either find a place to treat it for you, being such a large section, or use it as-is.  If you plan on upgrading your setup eventually anyway, money may be better saved/spent elsewhere.  Try putting a 2" piece of material in a gas forge and see how long it takes to heat up, might wanna have a book handy  : ).  4" will take significantly longer, if you are lucky enough not to damage something in the process.  Something that large being orange hot is going to radiate a significant amount of heat too and require a way of handling it.

Even mild steel will make an adequate anvil if it is a large section, especially starting out.  Annealed 4140 (which I imagine it would be, although it is possible that it is already hardened) is going to be harder than mild steel too.  Wouldn't hurt to use it as-is either, if it ends up being too soft for you you can always grind and file it down a little and then go the heat treatment route.

[caotropheus]

I know little about heat treating 4140 but I saw this as an homemade setup

 

 

You can test the 4140 block you have (in current raw state) with a ball bearing for rebound and see if it is ok. If you still decide to heat treat the block by your self, you can always dig a hole in the ground and make a big and deep enough coal forge.

[nicole]

Hi all,  I made a die set out of 4140 for my smithin magician to form tenons.  It worked pretty well on the first test..I did not heat treat it.  I was thinking that since the working end of the die would be getting so hot it wouldn't matter there and at least for a few tenons I made it still looks fine.  The striking end was beat up badly though and mushroomed like crazy which I ground off.  The question is if there is a heat treat recommended to toughen it up but still avoid spalling.  I was thinking of  an oil quench and tempering at 800F for 39RC making it softer than my hammer but tougher than annealed state.   The dies are 0.50" thick, 2.5" wide.  Ultimately I am thinking of going to go to a better alloy if this set isn't long-lived.. I have some S7 around but I want to use the dies and see how they perform for a bit before I use the more expensive material. 

Nicole

[Frosty]

Another solution is to use a soft hammer for striking this kind of tool, heck top tools in general.

Frosty The Lucky.

[BIGGUNDOCTOR]

I agree with Frosty, a hard lead, brass,or similar mallet would work good. But even brass will mushroom a soft steel over time. 

If it was me I would just heat the top edge to red, and quench in water. Polish, and heat to a straw / purple color, requench.

4140 should work fine. 

[nicole]

Thanks Frosty and Biggun; I do use a HF steel beater hammer but that's to protect my forging hammer..I need to get uniformly into the habit of keeping a forging hammer for forging.  I can try going to brass and the local heat treat

[Eddie Mullins]

You could also weld another piece to your top die so that you are striking it, rather than the die itself. I have a short piece of thick mild welded to my dies. I can dress as needed, or eventualy replace and the dies are none the worse for wear.

[nicole]

Eddie that sounds good too- if the working end of the die holds up well enough I can probably get a good long life with the striking end replaceable...

 

[VaughnT]

I agree with Eddie.  I love welding a kiss button on top of the die so it takes all the abuse of the hammer strike.  When it's thoroughly mushroomed, just chop it off and weld a new one on.  The die remains pristine.

[gearhartironwerks]

So, years ago, I asked Grant Sarver about heat treating 4140 and he suggested the manufacture specs. I said that they don't work and are too soft...i.e. quenching in oil and tempering. After a prolonged discussion, he admitted that quenching in water and not tempering was a better way to go. 4140 is a very forgiving steel and can also be quenched in super quench w/o cracking. Every smith needs to question the status quo and experiment based upon their needs.

john

[nicole]

Hi John, Vaughn thanks for your most recent comments.  I am leaning to the kiss block once I knock this dreadful flu!  But anyway in reviewing the comments I think we could start a new thread entitled, " how many ways can smiths find to screw in a light bulb? "  I think this is such a great part of IFI with so much experience and so many willing to share. Thanks. Nicole

[Charles R. Stevens]

Stone mason'hammers are dead soft, they are the short handled double headed ones that look like Thor's hammer. 

[nicole]

I think my HF hammer may fall into the category of dead soft; after dressing the face when I got it it did not take long for it to look really beat up..I did not think to pay attention to the sparks when I dressed it..need to take a look!

[671jungle]

On 1/7/2014 at 12:57 AM, Frosty said:

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.

this is impressive. I had no idea silver solder could be used for heavy applications. I can imagine the impact and torque at the teeth and silver solder will hold it together!?

[Frosty]

On 8/5/2019 at 6:29 PM, 671jungle said:

this is impressive. I had no idea silver solder could be used for heavy applications. I can imagine the impact and torque at the teeth and silver solder will hold it together!?

Yes, I replaced carbides on bits when possible for almost 20 years. I couldn't believe it the first time I saw one of the other drillers silver soldering carbides on a pilot bit and asked at the local Lincoln welding supply. If time allowed one of the guys would take you out back and demo or run you through a short course on products, techniques, etc. 

One of the videos was of a silver solder tensile test showing a yield strength of 35,000 psi tensile If I recall the number correctly and there were specialty solders stronger than steel. And impact strength was incredible, it deforms to a greater degree without yielding so rebounds intact.

Neat stuff. 

Frosty The Lucky.