4140 heat treatment

M

Matt River

Joined
Oct 1, 2012
Messages
126
Interested in some information on heat treat for 4140 for hand forged cleavers, hatchets, and shop tools. Not much luck so far searching, also wondering if thereis a thread with consolidated heat treatment "best practices" that I am missing.

Thanks, Matt from South Dakota
 
Found some basic information.
http://www.anvilfire.com/FAQs/heat-treating-4140.php

Still interested in methods specific to cutting tools. Differential hardening is of specific interest, clay or edge quench. Differential tempering also of interest. Looks like retains most quenched hardness at 400f temper, up to 55rc, assuming that at this hardness even 4140 would be brittle?
 
Page 226, ASM Metals Reference 2nd edition, it lists 1080 and 1095 with water quenched hardness 400f tempering as 57 and 58 HRC, 4140 is at 57 HRC as well but with an oil quench. With double the carbon the simple steels have the same approximate hardness but far lesser mecanical strength. Carbon content is often put forward as the only factor that effects hardness and therefore edge retention and cutting qualities. This does not seem to have any relation to actual ASM data. 1040 is at 51HRC at the same 400f temper, clearly the 4140 outperforms the simple carbon and, within the tempering limits used for blades 4140 is directly equivalent in HRC to 1080. Beyond this, most 1080/1085 blades are quenched in oil which would logically seem to produce a lower HRC. At equal 400f or 450f tempering, is 1080 somehow mechanically stronger or more elastic? This would seem to defy both logic and the actual mechanical performance charts.

If anyone can enlighten me I would greatly appreciate it.

Matt
 
Pretty much every discussion of lower carbon alloy steels involves dismissing steels like L6, S7, 5160, and especially 4140 in favor of "simple" higher carbon steels. It will take me a while to compile the comments from multiple threads but the basic message is pretty much always the same, high carbon is good, low carbon is bad no matter the alloy. The opposite holds true in discussion of steels above the eutectic point in general.
 
Here is a post where 1095 is consistently rated as better for a high impact hawk other than a couple votes for 5160 and real world experience from a smith using 4140 for axes. The idea that 1095 can have more or even equivalent toughness in comparison to 4140 at the same HRC does not make sense to me at all, maybe this thread is not typical, I will see what else I can find. http://www.bladeforums.com/forums/s...e-in-a-tomahawk?highlight=4140+heat+treatment

I guess that a secondary question that I have is if the eutectic point remains a constant in alloy steels, i.e. can carbides form either above or below .8% carbon in complex steels.
 
Eutectic point ?? They don't do a complete job to determine the eutectic. Kevin Cashen has a book where the eutectic is given three different numbers !! Remember that these graphs are "equilibrium " which is rarely obtained ! They are guides rather than complete , exact drawings !
 
Almost none of the people giving suggestions in that thread spoke about real world performance or actual experience using it as a tool. I would take that into account when reading people's opinions.
 
Have to admit that my own perception of issues with alloy steel use are incorrect to a certain extent, 5160 and 52100 are the real performers among alloy steels that harden enough for blades. 5160 and 52100 are both consistenly rated pretty high, they easy outperform 4140 and most all other alloy steel. The general reccomendations to use simple carbon 10xx steels is almost always linked to those starting out in making. 10xx steels are way easier to sharpen and file profile/grind so this makes a lot of sense. Have to admit that due to my own interest in both experimenting with materials and high impact choppers and axes I hope to acquire some of the seldom used alloys and see what happens. Looking at the charts I am picking out 4150, 8650, 8660, 9260, and in tool steels A3 looks very interesting compared to A2, .2% more carbon, less manganese (decreased forgeability?), big increase in vanadium to .8% up to 1.4%, equal toughness and even higher wear resistance. Given Gough's tests with A2 coming out on top easy this makes A3 interesting to me.

So far as alloy steels go I do not have a clue if, for instance, 9260 silicon Mn steel is foregeable or worksble at all, might be hot-hard or totally useless for any blade related purposes, still curious anyway.

So far as carbide formation question goes, maybe eutectic zone or "peaks" would better describe the general concept I am trying to ask about, just wondering in general about potential changes from alloy elements in the band or zone wherein carbides would begin to form due to the inability of the Fe matrix to hold any more carbon in solution when hardened under standard(ish) conditions.
 
Steel is all about trade offs, a gain in one side is usually a loss in another for the same general class of steels (low allow, medium allow, high alloy) Toughness reduces wear resistance, hardness reduces toughness. Its about finding what the most important and then working with the process to get the most of what you can out of the other parts.
 
My suggestion would be to use 5160 instead of 4140.



4140 is designed for toughness. While it would not chip, it would have a poor edge retention. Anvils and hammers are good uses of 4140. Knives and cleavers are a good use of 5160.
 
Thanks for the reply Stacy. My curiosity in regards to 4140 will only be satisfied through testing of hardening response and cutting tests :) 5160 actually has a bit greater tensile and yield stength than 4140 in addition to way better edge retention and other blade qualities. 52100 gives up a little toughness with greatly enhanced blade qualities, analysis of the alloy steel charts really does not bring up many contenders with 5160 or 52100, but I will continue to work with 4140 as I am making anvil tools from it and hope to make some forged hatchets, axes, etc. My cleavers are not necessarily for camp or bush use, they are meat cleavers and preliminary tests are showing the 4140 to have a bit of an advantage over my simple steel forgings.

Still interested in knowing more about complex carbide formation and the changes in carbon retention in the Fe matrix due to alloying elements. D2 for instance forms carbide components that make up a substantial percentage of mass when quenched, pretty much add up the totals for all alloying elements to equal the fraction of carbides in totality. Chromium at lower fractions seems to increase both toughness and tensile strength but clearly at higher concentrations it has an opposite effect, Vanadium refines grain and according to research on wootz blades it starts to actively effect the qualities of the steel and pattern formation at around 50 parts per million.

Although reading and researching basic metallurgy texts is probably not going to improve my cutlery techniques I do feel that there is a lot to be learned about blade steels that is never mentioned by makers. Many of the tool steel do not require normalization for any use, and multiple steels in common use for blades such as W2 are supposed to be heated up slowly for hot work. A propane forge heats very fast, and a coal/charcoal forge can be used very differently than a propane forge which only heats steel at pretty much one speed. Many people experience failures with W2 blade forging attempts even though they quench in oil. I am not yet an expert on best practices in complex steels for thin cutting tools, but what I am actually seeing is a one size fits all rigid doctrine that seems to have developed outside of standard metallurgy. Any sort of conflicting opinions are often ridiculed and minimalized in favor of either personal methods or standard practices. In many ways my methods are probably as far removed from "good" metallurgical practices as is possible, and stock removal with foil envelopes and programmed fully controlled heat treatments being actual best practices, but I am still curious and maybe someday I will have salt pots and a nice kiln and improve my methods from cave man blacksmithing.

thanks, matt
 
9260 ? think 5160. Both have major use as automobile springs . 9260 also has been used for fencing swords !!

4140 is one of the better alloy steels out there many uses ,fine balance of strength, toughness ,cost ,ease of HT.

Anvils , hammers , axes are fine uses for forum members.
 
James Helm, Storm Crow here on BFC, makes his tomahawks from 4140 and does his own HT. Perhaps you should drop him a line.
 
jdm61 said:
James Helm, Storm Crow here on BFC, makes his tomahawks from 4140 and does his own HT. Perhaps you should drop him a line.
Click to expand...

Hey, it's that guy I am! :) Shoot me an e-mail, Matt, at helmforge@gmail.com . I keep things pretty simple, and you may want to vary from what I do, but I can at least give you a bit of an idea.
 
Actually I tried to email you first Mr Helm :) Really like the hand forged axes that you have made, my email attempt probably did not work. Have also watched your video of routering out the tactical hawk poly micarta blanks, very good video. Intent with the 4140 cleaver idea is bone cutting on hanging carcasses, butcher tools.
 
Part of my interest in the potential cutting qualities of 4140 is making carpenter's "hacking" knives of my own design. Many carpenters now carry chisels, a poor substitute for a real hacking knife. In addition to endcstrikes and use as a chisel, a hacking knife is traditionally struck from behind the blade on the spine of the knife. Toughness and some edge holding are needed along with a nearly annealed spine to allow for hardened hammer strikes. Yes, I am also experimenting with 5160 andvtool steels. Also working on catspaws and several types of trowel and mini-shovel metal detecting recovery tools. Have been using some old bed frame angle, forged round for handle socket and flared for diggong end of trowel. For production I will buy 1.5"x1.5" by 1/8" angle in appropriate and "tough" steel, 5160, 4140, and other steels uncommon to normal bladesmithing will be tested before final selection. Edge retention for some of these products has to compete with toughness and annealed impact strength, spring qualities, hammer blow safety, lots of factors.

thanks, matt
 
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