Heat Treated 4140

mooncoon

mooncoon

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I was in Budget Steel a few days ago and asked if they had annealed 4140 steel; answer was no they only had heat treated 4140. Fellow behind the counter had no idea what if was nor even what the numbers mean :>(
They apparently sell both annealed and heat treated although had no annealed in stock. So the question becomes; does anybody know what Budget Steel might mean when they refer to heat treated 4140 steel beyond the fact that it is 4140 steel?

cheers mooncoon
 
Could be that they refer to 4140 HTSR. Heat treated, stress relieved. A little tough to work with but also with good properties. I work with lots of this stuff at my day job. 4140 is also a chrome/moly instead of a carbon steel like 1045.
 
As ripstop said. Most 4140 (aka SPS) is sold in a heat treated state that gives it very good durability qualities and a RC hardnes around 28-32. Tough stuff and widely used for machine parts. We go through tones of it a year. You can buy it in the annealed state which is full soft (well, for steel) and then you can heat treat it up to RC 56-8 or so. You loose some toughness but get better wearing proporties. Ideally if I was going to do this, I'd switch materials to 8620 (Impacto) and get it carburized to give me the hard case for wear but softer core for toughness. Both steels have been much used in gun makeing, though 4140 is more used today becasue it's bought pre heat treated and saves money that way by not having to go into heat treat again like 8620 does after machining. That being said, you'll get a slicker bolt action from the 8620 as you can polish the bolt track quite highly and it will retain the finsh longer then the softer 4140. Over all the 4140 is stronger though. Any of this help? If you want to know exactly what the numbers mean I have to bring my machinery handbook home from work, can do if you want, or do a web search for ANSI standard steel labeling.
 
My concerns are basically is the heat treated so hard or so tough that I will find it very difficult to work with using non carbide tools and files. My intended use for it would be partly for internal lock parts in muzzle loaders, particularly tumblers and partly for a falling block reciever. Both uses involve a fair amount of filing and I am left with the impression that I would probably have to anneal the steel first. I don't think the reciever would have to be re heat treated while the tumblers would have to be tempered and hardened whether from annealed or from heat treated material.

thanks mooncoon
 
The whole idea about using 4140 or 4130 in the heat-treated state is that you do not have to go trough the hassle of heat treatment after your part has been machined.
30 RC hardness, and with a tensile strength of 150,000 it would be sufficient for most parts which are required to be made out of this type of material.
In addition, it can be machine without too much of a problem, but good cutting tools and cutting fluids are necessary.
 
You can file the 4140 HTSR fairly easily. If you case harden your finished parts up to about 45 RC, you will have a problem dragging a file over it. This hardness goes about 2 mm/.08 thou. deep and below that you still have a average hardness of 30 RC. I don't think you would want hardness to top 45 RC for firearm parts.

To machine 4140 HTSR, keep the feed to it just like 1045 but drop the spindle speed about 20% of 1045. You will find working with it very manageable. You must do all finished machining before final hardening unless you really like working with carbide stones. You definately do not need to anneal 4140 HTSR before working with it.

I would prefer using 8620 (impacto) but 4140 HTSR is so common that my work throws out enough endcuts to fill my home machining needs. :)
 
I think for your internal lock parts you are better off with a carbon steel or even a case hardened mild steel. In this case you are hardening for wear charactaristics and smoothness and are less concerned with strength. Actually, an oil hardening drill rod is ideal for this type of application.
HTSR 4140 is stress relieved at around 1150 degrees (F) which is hot enough to make it pretty easy to machine. You wouldn't have to anneal.
4140 cannot be truly color case hardened because it will harden too deeply and stress cracking is likely to occur. I saw the results of an attempt to case harden a 4140 receiver and it was not a pretty sight.
4140 is a good choice for a falling block receiver if you don't intend to color case harden it. If you do, you are better of to make it from a mild steel or mild alloy like 8620. Regards, Bill.
 
Who needs some 8620? I have about 30 feet of it in 5 inch diameter. One peice is a 20 footer. Now a 5 inch dia action would be cool. You could hang any profile barrel off it and not worry about it bending the action.
 
Maynard, cut it into 2 inch slices and you'll have a lifetime supply of gongs! :shotgun:
If you were anywhere near me I'd hit you up for some of that, but oh well... Can't get my lathe back until we get a garage again anyways.
Drew
 
Leeper said:
I think for your internal lock parts you are better off with a carbon steel or even a case hardened mild steel. In this case you are hardening for wear charactaristics and smoothness and are less concerned with strength. Actually, an oil hardening drill rod is ideal for this type of application.
HTSR 4140 is stress relieved at around 1150 degrees (F) which is hot enough to make it pretty easy to machine. You wouldn't have to anneal.
4140 cannot be truly color case hardened because it will harden too deeply and stress cracking is likely to occur. I saw the results of an attempt to case harden a 4140 receiver and it was not a pretty sight.
4140 is a good choice for a falling block receiver if you don't intend to color case harden it. If you do, you are better of to make it from a mild steel or mild alloy like 8620. Regards, Bill.
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True, 4140 thru hardens or not at all (if you want a good product) A2 is nice for sears and related parts though, very hard, can take a heck of a polish and wears well. Thru hard again though, go 8620 or carbon if you want a case as stated....
 
The 4140 signifies that this is a 4100 series nickel chromium low alloy steel (less than 1% each of Ni & Cr) with a nominal carbon content of (40/100)%.
Fully annealed 4140 has a tensile strength in the 40,000 psi range, and heat treated (quench and tempered) 4140 can range any where above the annealed strength up to a maximum of about 220,000 psi tensile strength with no tempering after the quench; however this is far too brittel for most practical applications. The tempering part of the heat treating operation is a time/temperature relationship that is the determining step for the finnished strength and ductility requirements for the material. This will be dictated by the mechanical performance requirements of the the application useage. For instance, modern 4140 high power rifle barrel blanks are normally quenched and tempered to render the material with a tensile strength in the 120,000 to 140,000 psi range; strong enough to handle peak working pressures of 60,000 psi with a reasonable safety factor, but not excessively brittle so as to splinter to pieces when subjected to the rapid load rate upon firing.
 
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Ripstop said:
I've made a mistake in terminology. Where I stated 'case hardened', I meant to say surface hardened. There is a difference as many know. Sorry about that. :redface:
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Actually, just to cloud the matter for you, case hardening is a surface hardening process, yeilding a "case" of hard material anywhere up to .100 of an inch thick, down to .01 or less. The core stays softer and tougher, supporting the hard skin over it. Through hard means the material is hard all the way thourgh.
 
4140 is chromium molybdenum not nickel chromium. Also the tensile strength of annealed 4140 is more like 100,000psi with a yield of around 70,000. HTSR4140 takes these values up to 125,000 and 100,000 respectively.
I believe EN30B is what would be considered to be a nickel chromium alloy. It contains around 4% nickel, just over 1% chromium and a bit less carbon than 4140. It is somewhat stronger and a bit more difficult to machine but is a good shock load handling material. I recently made a bolt for a Remington 700. I made the body of C1045 with the extraction cam and bolt handle base integral. The bolt head I made of EN30B. The head attaches to the body with a pin much like on a Savage. More work than it's worth, really. Way easier to simply buy a bolt from Dave Kiff!
I found I was able to carburize and case harden EN30B with some degree of success. I could also carburize and case harden 4140 but it was very difficult to achieve the results I wanted without stress cracking. Keep in mind, carburization turns the surface of the 4140 piece into something more like 4180. A warmed up oil quench seemed to work out fairly well.
The bubbling water quench necessary for colour hardening will destroy a 4140 piece.
 
Kudo's to your ingenuity, but putting a case on 4140 is a bit like putting butter on cheese eh? Why not just use 8620 and be done with it?

Leeper said:
4140 is chromium molybdenum not nickel chromium. Also the tensile strength of annealed 4140 is more like 100,000psi with a yield of around 70,000. HTSR4140 takes these values up to 125,000 and 100,000 respectively.
I believe EN30B is what would be considered to be a nickel chromium alloy. It contains around 4% nickel, just over 1% chromium and a bit less carbon than 4140. It is somewhat stronger and a bit more difficult to machine but is a good shock load handling material. I recently made a bolt for a Remington 700. I made the body of C1045 with the extraction cam and bolt handle base integral. The bolt head I made of EN30B. The head attaches to the body with a pin much like on a Savage. More work than it's worth, really. Way easier to simply buy a bolt from Dave Kiff!
I found I was able to carburize and case harden EN30B with some degree of success. I could also carburize and case harden 4140 but it was very difficult to achieve the results I wanted without stress cracking. Keep in mind, carburization turns the surface of the 4140 piece into something more like 4180. A warmed up oil quench seemed to work out fairly well.
The bubbling water quench necessary for colour hardening will destroy a 4140 piece.
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When case hardening is done, it's done primarily to achieve better wear charactaristics or to reduce friction. Why not use 8620? Because 8620 might lack sufficient strength for the job at hand. In general it is right to choose a mild steel anytime case hardening is planned. Sometimes though, you might want to try and achieve better wearability with an alloy steel for the strength it provides. Keep in mind a particular material might be the one used just because that's what's available too! Regards, Bill.
 
Leeper said:
When case hardening is done, it's done primarily to achieve better wear charactaristics or to reduce friction. Why not use 8620? Because 8620 might lack sufficient strength for the job at hand. In general it is right to choose a mild steel anytime case hardening is planned. Sometimes though, you might want to try and achieve better wearability with an alloy steel for the strength it provides. Keep in mind a particular material might be the one used just because that's what's available too! Regards, Bill.
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Good point, if you don't have it, it ain't much good....(if you do want a nugget of 8620 let me know, we have some laying around and we don't use it often). And I didn't mean to sound as if I was dissing you, getting creative is the only way to learn if you can do something despite conventional wisdom (which often enough just hasn't tried it).
 
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