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radkins
12-21-2013, 10:00 AM
I just bought a 4140 H/T bar end from a steel shop through E-Bay that is described as 28-32 RC, 8" diameter x 2" thick and I was wondering just how much of this piece is actually going to be in the 28-32 RC range? I would think an 8" bar would only be that hard near the surface with the center being somewhat softer (in an annealed state maybe?) but is that correct and if so just how deep would the hardened material extend?

loose nut
12-21-2013, 10:39 AM
I would think (and I try not to) if the heat treating was done properly it would be the same all the way through.

Rosco-P
12-21-2013, 11:22 AM
I agree with loose nut, if the soak time at temperature was correct, the steel would be uniformly hardened.

radkins
12-21-2013, 11:56 AM
That would be really good, somewhere I read, heard or maybe dreamed that large diameter H/T bar or thick plate was only hardened a certain depth near the surface. Not a thin layer like case hardening of course but softer toward the center. I honestly don't know where I got this idea.

jlevie
12-21-2013, 12:07 PM
If the heat treating is done properly, a 2" bar should be essentially the same hardness throughout.

radkins
12-21-2013, 12:12 PM
If the heat treating is done properly, a 2" bar should be essentially the same hardness throughout.


That was my understanding but these pieces are from a bar 8" in diameter.

jlevie
12-21-2013, 01:20 PM
I may have misunderstood. I thought you meant the the piece was heat treated after cutting.

If the piece was cut from an 8" round after heat treating, how uniform the hardness will be will depend on where it was cut from the bar. If from at or near an end it should be pretty uniform, but if from the middle maybe not so much.

Jaakko Fagerlund
12-21-2013, 01:36 PM
If you know the manufacturer of said bar, they usually have data sheets on their website that give you nice graphs of how the hardness vs. thickness vs. depth goes. Some materials will harden uniformly, while some others will start to give soft results above certain diameters. It all relates to the materials Jominy test results.

cuemaker
12-21-2013, 02:23 PM
4140HT is supposed through hardened, as it can be used as a base material for lots of material specs...ASTM this..ASME that...etc

Leadfootin
12-21-2013, 04:48 PM
If it is anything like the piece I got from Metal Supermarket a couple months ago it will have soft spots, hard spots and little inclusions which spark when they eat your carbide insert!

After on attempt I bar-b-que normalized it and most of the problems were minimized. Off-shore imported steel at a "good" price is no steal at all.

iMisspell
12-21-2013, 06:21 PM
I just bought the same thing 4140-HT 8" dia, 2" thick from speedymetals (about $100). Im hoping to cut into it by next weekend, i can post back how it cuts if you want. After reading your post here, i was/am tempted to bring it to work and see what it read on the tester they have in QC (going through alot at work and working in and then out of the building with a chuck of stock that size might cause a problem).

rickyb
12-21-2013, 08:26 PM
I just bought a 4140 H/T bar end from a steel shop through E-Bay that is described as 28-32 RC, 8" diameter x 2" thick and I was wondering just how much of this piece is actually going to be in the 28-32 RC range? I would think an 8" bar would only be that hard near the surface with the center being somewhat softer (in an annealed state maybe?) but is that correct and if so just how deep would the hardened material extend?

An 8" bar won't quench down more than about 1.5 to 2" from the surface. Maybe not even that deep. Too much depends on where the bar is in its chemistry range and the severity of the quench. It just is not possible to remove the heat from that much mass. The only way to get uniform microstructure and hardness is to quench and temper a 2" slug as you purchased. What are the chances that they cut 2" off of a bar, heat treated it based on it's chemistry and certified it before sending it to you. I'd say zero.

So what you have is in essence a surface hardened part. The core properties will be significantly lower in yield strength and toughness. On the brighter side the core won't form those nasty and tenacious burrs and you won't break taps so easily.

radkins
12-21-2013, 09:31 PM
Ok that's about what I was thinking but I guess I was just hoping it went a bit deeper than that, it occurred to me after ordering that the entire piece might not be hard. Oh well I will probably still be able to use it for something and it cost me less than $30 even with shipping.

becksmachine
12-22-2013, 01:12 AM
Maybe relevant, maybe not, quoting from the Ryerson stock list;

"Properties are at the center of bars up to 1 1/2" and at half radius of bars over 1 1/2" "

"41L40/50 H.t. over 4"-8" Br269-331 R27/35

Dave

radkins
12-23-2013, 11:19 AM
My piece of 4140 H/T arrived today (it was delivered USPS by a groaning lady mail carrier, Lol!) and it turns out it is indeed a piece sawed about 2" from the end of the bar with one sawed side and the other side being the raw bar end. My question is does this mean that it should be evenly (roughly anyway) hardened throughout since even the center of this disc would have been within 2" of the quench? It would seem so and my primitive hammer/chisel method of hardness testing seems to indicate it is.

rickyb
12-23-2013, 09:11 PM
My piece of 4140 H/T arrived today (it was delivered USPS by a groaning lady mail carrier, Lol!) and it turns out it is indeed a piece sawed about 2" from the end of the bar with one sawed side and the other side being the raw bar end. My question is does this mean that it should be evenly (roughly anyway) hardened throughout since even the center of this disc would have been within 2" of the quench? It would seem so and my primitive hammer/chisel method of hardness testing seems to indicate it is.

I'd say you have a fair chance of a uniform part.