OT steel question

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My father and I recently purchased some firearms. I've had a lot of time on my hands lately and it got me thinking. If gun barrels are able to get hot and cold multiple times without ruining their heat treat, why don't we make knives out of gun steel or use their heat treat protocols? Is it a hardness issue? Edge retention? I'm sure there's an obvious answer but I'missing it. Any help?
 
E,
Interesting topic. Many of the steels used for barrel making are also used in knife making. I think it boils down to: intended purpose of the object, how the object is made, and the desired hardness (affected through heat treat; which also affects edge retention, brittleness, and maintainability). Now, knifemakers, correct me if I'm wrong here, but I'm pretty certain that all a barrel blank is really nothing more than round bar stock of something like 4130, 410, etc that is cut, drilled, and milled. While the barrel changes shape vis a vis machining, it is not changing form (ex. being flattened, or made into a square of bar stock). The knife on the other hand, starts life as a bar of steel, that through heating and a LOT of impact is further flattened and transformed into a shape very much unlike the starting bar stock. In order for this transformation to occur, heat is added to increase the malleability of the metal and make it easier to work -- the hard part here is that the heat affects not only the steel's malleability, but also its tensile strength, and material composition at a molecular level (crystallization point). To accommodate the molecular changes made by the heat introduced during the forging process, the knifemaker is required to heat treat the knife once it has taken its final shape to ensure that the steel is re-hardened to a suitable state for an impact / cutting tool. So, bottom line (IMO; I could be completely wrong here ;)) is that barrels are (probably) made from automatic / continuous hot forged stock that has been HT'd during the manufacturing process and then milled / machined to take their final form. Knives are open-die drop forged (drop as in dropping a hammer on the steel atop an anvil), and are molecularly changed a few times during the process; again to affect malleability during the forging process, then again during the HT.

Again, I might be 100% wrong and I would defer to a pro, but from a brown bag mechanical engineering standpoint, I am fairly confident in answering your question in that: the steels used can be one in the same -- the difference lies in how the raw stock is transformed into its final product.
 
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Thanks Will. I think I understand what your saying as far as manufacturing goes. But I have a couple of questions. Some knife makers (I think Andy included) don't forge with a hammer and anvil, they use a grinder to remove stock from the bar. Again, I could be way off base there, but I have had a knife that the maker made using "forging" and they look completely different. Does Andy heat his knives after grinding because of the heat applied during the grinding process?
Second, and the more important one to me is, why are knife makers so concerned with what you do to your knife when it comes to heating (on some cases voiding a warrantee) but a gun barrel get hundreds of degrees hot literally thousands of times and it doesn't change its performance. If we made a knife using a CNC machine and never forged or grinded it could it then be as heat tolerant as a gun barrel? I guess I'm asking "Why are knives so temperature sensitive". Sorry if you answered that above and I missed it. Obviously I'm not an engineer and if I was better at chemistry I would likely be Dr. than a RN, lol. Thanks for your help.
 
Second, and the more important one to me is, why are knife makers so concerned with what you do to your knife when it comes to heating (on some cases voiding a warrantee) but a gun barrel get hundreds of degrees hot literally thousands of times and it doesn't change its performance. If we made a knife using a CNC machine and never forged or grinded it could it then be as heat tolerant as a gun barrel? I guess I'm asking "Why are knives so temperature sensitive". Sorry if you answered that above and I missed it. Obviously I'm not an engineer and if I was better at chemistry I would likely be Dr. than a RN, lol. Thanks for your help.

There is a huge difference between a gun barrel and a knife. Yes they are both metal, but that is about the end of it.

1- a gun barrel needs to exist and be whole, that's it. A gun barrel is thick steel, not a thin, refined edge.

2- knife steel must be able to be ground VERY thin and retain it's strength. Knife makers are concerned with what a knife goes though because they heat treat it after the primary grinding is complete. They purposely do not let their steel get hot to maintain the heat treat and temper. If the blade steel has been exposed to heat, those factors are altered.

The short of it is a gun barrel does not have to be a very thin edge that holds it sharpness without chipping and rolling. Sure a knife can be made out of steel that is not for knives. But, in the end, it wouldn't be a very good knife.
 
Thanks Shmittie, this makes sense. A knives thickness (or lack there of) just makes it more vulnerable.
 
Intersting topic and I will answer as much as I can, but these are my opinions, so bare with me.

As far ad the grinding is concerned, all of the profiling, drilling, primary grinding is completed prior to heat treat while the steel is still in the annealed form. The steel at this point is much softer and easier to grind. While we are grinding, the steel never gets up to critical temp (wouldn't remotely be able to hold it), and even when we quinch while grinding, it doesn't effect the steel.

When we grind post heat treat, we do have to be careful not to overheat the steel. If we were to overheat post heat treat, the temper or draw would be ruined and hardness would be ruined. When doing post heat treat work, we are constantly cooling the blade.

As far as steel types are concerned, there are several factors, not limited to metallurgy, but also to end user preference, how the steel works for the maker ( for instance, It is much easier for me to grind stainless after heat treatment with a hollow grind vs. doing a convex grind) and current "hype" surrounding a steal. Some end users prefer tool steel like O1 and the patina that will form, while others prefer a more all weather like com154.

I am not completely familiar with the hardess levels used in barrels. Also, you wouldn't want to overheat a barrel, as it can warp and such.

I hope this helped at least a small bit, my mind is worn out already today and I have several knives to profile tonight!
 
Thanks Allen. Roughly, how hot can a blade get before you compromise he heat treat? I have an image in my head from Rambo II where they stuck his blade in hot coals and it came out glowing. Certainly that would do it right? But if I used it to dangle a pot or something over a fire 12 inches or so, for example, and it was hot to the touch, could that do it?
 
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Different jobs require different steel. A cold chisel has to be hard enough to cut, yet soft enough to not chip or break. The hammer that drives the chisel has to be hard enough to not badly deform, yet hard enough to drive the chisel. Gun barrels need to be hard enough to maintain the bullet's path and not wear at a high rate, but still can be bent. A knife has to maintain an acute geometric angle at work, but not chip or break at the point of use. All steels are alloys and it's the different additives that specify the best usage for the steel. Knife steels have a high carbon content which lets it be heat treated specifically for blade use. Stainless steels have high carbon and other additives to resist stain and oxidation. A quick search will get tables that show the varying mixtures in knife steels. These different ratios/mixtures also dictate how the steel will respond in use. Examples: 1095 is a "spring" steel, used in making springs, great knife steel for kitchen knives. 01 is a tool steel, used in drilling rod and other die tool applications, great knife steel. 1084 is between those two, used in many older farm implements, John Deere drive shafts, etc., great knife steel. The stainless steels have the same points of usage in their molecular design, think surgeon's scalpel vs. an industrial roller bearing.

The crucial point in blade making is the heat treat. At this point the steel has to be hardened (heated and quenched) to the point, that if dropped, it will shatter like glass, then heated (tempered) at lower temps to let it retain a cutting edge yet stay tough and chip free during use. Lots and lots of science behind all this, but humans have been doing it since we crawled out of the Iron Age.

In the movies when you see John Rambo, or some other hero, stick that knife in the fire, get it red glowing hot to cauterize a wound, just remember that he just ruined any heat treat. Might as well use it as a short ,flat club. Heating knife steel to the point it shows color (bronze, blue, purple) will pretty well destroy the heat treat.

Forging a blade is interesting and fun to do, IF you like that sort of thing. Stock removal is also fun and interesting, IF you like that sort of thing. Both methods will produce great blades with the caveat that the proper heat treat is done in both cases. Which is potentially better has been argued to death for years and I'll not add to that here.
 
Interesting topic huge and diversified in complexity at that. RLo put it pretty simply and straight forward - different steels were designed and configured for different purposes. Not saying that some gun barrels were not made from blade worthy steels, anything is possible, but most are not. Blade steels whether simple high carbons or alloy mixes are designed to get hard and hold edges for their "occupation" so to speak. They get harder than one would want a barrel to get. You bend a good blade it will eventually fracture and/or snap a barrel will just bend. Thermal conditioning and alloy content are used to make the steels preform as needed. A high carbon steel can potentially get to brittle or too soft depending on what a barrel of a gun will experience in use, therefore either shattering or bending from all the thermal cycling that takes place.
Not good!
Barrel steels are alloyed to withstand these thermal cycle shockings and maintain their function during use. Whole different ball game in steel characteristics.
Bottom line - Can you make a knife out of a gun barrel steel? Sure
Can you make a good knife out of gun barrel? Not very likely
The converse is true with knife steels to barrels.
 
I am not proficient at all about it but simple search in Google give me this:
How is a gun barrel heat treated?
link
http://ingunowners.com/forums/general-firearms-discussion/113039-how-gun-barrel-heat-treated.html

couple citation:

I've read a lot of guides on how to make your own barrels, but nothing about the proper heat treat/tempering for them. Anyone know something more than nothing about this?

I work for a company that heat treats steel bar, and some of our customers are firearm manufacturers. We get the steel in lengths of 20+ feet and ship them out roughly 8-12" shorter. It's easier to ensure a uniform hardness when the steel is processed in bar stock. The stock is then cut to length and machined into a barrel.

As the button is pulled down the bore and impresses the grooves and lands, metal is displaced. This causes stress in the metal, which can lead to inaccuracy, such as bullets walking off the target as the barrel heats.
Heat treating relieves that stress. Lilja worked as an industrial engineer for the John Deere Company in Iowa before he started in the barrel business in 1985. Part of his time at Deere was spent in the heat treating department. Lilja used to heat treat his barrels himself in a small oven in his shop. His increased production over the years, though, has made it easier to send out the barrels to Spokane, Washington, for heat treating.

Barrels are heat treated to relieve stress from the rifling and threading and other manufacturing processes. Not hardened like receivers on bolt guns.

Hardened steel can be cut with a hacksaw. Just because steel is hardened doesn't mean it's indestructible. Carbide and tool steel are harder than barrels, and explains why you can cut them.

I operated a heat treat furnace for about 5 years, that was 20 years ago.
In general we heated forgings in a 1600 degree furnace that moved on a belt toward the quench for 50 minutes.

After the quench the forgings continued on a belt and were reheated in the draw furnace for about 50 minutes at a temp anywhere from 1100-1400 degrees. The whole process took about 2.5 hours.

Using a Brinell Hardness tester, forgings were very hard after the quench and much softer after the draw. The draw readings were the most important.

I have my precision rifles cryonized "spelled wrong" put in a chamber to -300f it make the gun shoot straighter and improves barrel life.

Steel barrels (not stainless steel) are heat treated and stress revealed after machining and rifling. A mill spec M16/M4 5.56 barrel is hardened to around 30 Rockwell C scale (i think the exact specs are 28 to 33 Rockwell). So technically they are "hardened" but not to the extent that most people think of hardened steel. 30 Rockwell is saw-able and file-able but much stronger than regular steel (which can vary from 3 to 12 Rockwell depending on type). The mil spec barrels are made from chromoly steel usually the 41xx series of alloy steels.

For a comparison, most steel disc targets are hardened to around 52 Rockwell, which is still sorta file-able but is very hard, If it was taken to 60 Rockwell you would pretty much roach the file.

Assuming the barrel you are using is made of the 41xx series of alloys then heating it to anything above 500 degrees could have adverse effects.

Here is a PDF that compares Brinell to Rockwell. www.universitymachineservices.com/rockwell.pdf


and so on

I am not sure that I understand a half what they talking about, but button point is:
yes barrel's are heat treated. they put to Rockwell hardness around 30, which I assume done to preserve plasticity - returning to initial form when bullet is out and barrel is colling down.
if I understand correctly they heat treat relatively big peace for uniformity and then drill and grind several barrel's from it.
I do not think it to hard with steel as soft as 30 compare 60-65:)

my husband was showing me a utube movie about bullet going through the barrel in slow motion from Remington 700 rifle
the barrel bend like crazy. it really amazing. that why the newest Remington 700 has a barrel of triangle shape in perpendicular cut instead of classic round one - they claim that this increase stability of the barrel.

so basically all the same depending of task:
both barrels and knives are heat treated

heat treatment depend of task:

for barrels you need strength and toughness - do not crack and terrain the from

for knives edge retention, stain resisting and so on

if you pay attention they mentioned that some other part of rifle or gun also heat treated but to different degree hardness depending of task
 
I also was looking for which type of steel they use for barrels

non-stainless:
41XX
mainly 4140, C 4140

stainless 416

4140 is used for knife making mostly for axes, tomahawk and big thick "survival", Camp type of knives, machete and so on
though it usually heat treated around 55 Rockwell for knife purposes
I think throwing knives will be decent from it

for example this tread
http://www.bladeforums.com/forums/showthread.php/998401-6150-vs-4140-steel

416 stainless could be used for knives
I f you see very crappie, very cheep around 30 cents knife "made in China" it could be 416, though most likely 420 or 440A

couple citation about stainless vs non stainless steel use in barrels :

- My Favorite gun guru, who made and built barrels and rifles, tested, tested to destruction and then sliced diced and analyzed the results.

Made the claim "that Stainless barrel's are over rated because to use a grade that would do what was being claimed could only be done with a grade that would result in ten times or more the cost of tooling used in barrel making or then any carbon steel did or does."

I am sure there are grades of steel and stainless steel that would be very good barrels, maybe even better then carbon steel alloy's if the cost of machining the barrel is not cost prohibitive.

- A slightly alloyed carbon steel like a 4140 even pre-hard stuff to 34Rc cuts like butter compared to a good stainless.

- There are a million alloys out there and I'm sure if you started with plain carbon steel (1018)and began adding alloying elements to improve things like wear and notch resistance, strength, corrosion resistance, etc, you would end up with something both impractical to machine and too expensive to justify.

- Everything is a compromise. A Chrome lined, Cro-moly barrel is probably the best balance of all things but as someone said you probably won't notice a drastic difference in a lifetime.

- Currently a popular advertising gimmick is listing AR-15 barrels as "Chrome Moly steel".
The barrel is made of a type of steel known as a chrome moly, but the intent is to make the unwary buyer think he's getting a chrome LINED barrel when all he's really getting is the same 4140 chrome moly steel that's been used by gun makers since at least the 1930's.

- There's a huge difference between the stainless alloys that were available 50 years ago, and even more difference in the knowledge of how to build a stainless barrel.
50 years ago stainless barrels were almost unheard of, and were hard to come by. Quality was suspect.

All we can do is go by the real experts, the bench rest and Match shooters who buy the best custom barrels money can buy, then shoot them until the accuracy starts to degrade.

On the bench rest and match ranges you see just about nothing but stainless barrels.
If carbon steel were as good as, and lasted as long as stainless, these people would have figured that out and you'd be seeing carbon steel barrels on the line.
You don't.

Shooters at this level don't buy into stories or interesting theories. They go by actual results proven over years and thousands of shots.
A good carbon steel barrel will shoot as good as a stainless, but it won't maintain that accuracy as long as stainless.

------
beginning of instruction how to make barrel:
link: http://www.wikihow.com/Make-a-Gun-Barrel

Choose the type of steel to be used for the gun barrel. The steel chosen must have a strength of 100,000 psi (689476 kPA) to withstand the explosive force of the charge that propels the round. The steel should have a hardness of 25 to 32 on the Rockwell scale so that the steel is strong enough to contain the explosive charge, but not so brittle that it will be harmed by the machining operations to be performed. Obtain 1.25 inch (31.75 mm) rods from a specialty steel mill. Ask for a quality certification on the steel. Specify that the steel must be stress relieved at the steel mill. •Select 4140 chrome moly steel. Chrome moldy steel is the least expensive alternative. It also is easier to chemically blacken, if desired, to give a traditional look to the barrel.
•Decide on 416 stainless steel. Stainless steel is more expensive than chrome moly Steel. Stainless steel barrels have a longer service life and are more accurate than chrome moly steel barrels.

I hope it help
 
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