Metal Question, Cold Vs Hot Rolled

[customizedcreationz]

Some interesting info here.

[brickeyee]

I know this, if my purchasing manager ever orders 200 feet of 2x2 cold rolled solid again for spreaders in the fab shop, i will choke her. it was a wee higher than hr.

Probably received an 'atta boy' for saving a few $$ on material costs, only to eat up more $$ on tooling and labor.

[HiBC]

I have a few suggestions.

As someone else mentioned,steel suppliers often will have a reference book describing steels.

McMaster-Carr is an outfit that sells reasonable sized lengths of alloy steels.

8620 is an alloy one might select for firearms parts.That is what a Garand reciever and many other gun parts are made of.Reasonable hardness can be achieved through a heat/quench/draw process,and it takes case hardening.

P-20 mold steel,and ETD 150,and ETD 180 are pre-hardened as I recallto about R 24-28 C(this is a ballpark number,I am not checking refs)
Now,thisis about as hard as 1911 frames and slides.ETD stands for Elevated Temperature Drawn,150 and 180 are the tensile strengths(150,000 and 180,000 psi.It is a Ryreson steel.

These steels are quite machineable,and may seve many purposes unheattreated.(Not sears,etc,but maybe a low pressure reciever)

Heating and quenching,along with warping and cracking,are avoided.

Expensive and maybe had to find,17-4 PH is a pretty magic steel.Precipitant hardening,it can get up(by recall) close to a Rockwell 40C by just holding it at 900 f for a couple of hours and aircooling.Please get better info,but this is a lead to send you looking.

I'm pretty sure that is what outfits like Freedom Arms use.

If there is a local plastic injection mold shop,ot if outfits like DME and Manhattan Supply still sell mold components,Core pins a a great resource.They are made of H-13 tool steel,through hard,tougher than a woodpeckers lips,and machineable with carbide Two hardnesses,also.

If themold shop has junk mold plates,some are 4140.

[Only S&W and Me]

Too much mis-information here...let me clear a few items....I'm 22 years in the biz Automotive Metallurgist.

Cold rolled steel is just what is says, steel cold reduced to provide better dimensional results and a elongated grain structure which provides it higher mechanical properities, especially in the transverse direction - across the grain direction. Typically carbon is low, under .10% but can be bought to higher levels for more strength. Higher carbon is harder and more difficult to form/bend.

Hot rolled is more common steel, like it says, hot reduced to a select dimension and lower strength than cold rolled (cheaper and typically worse surface finish than cold reduced but depends on the final pickling process).

Heat treatable steels are typically .30 and up carbon alloyed for hardenability depending on the section to harden deep (ie 4140, 4340). These are quench and tempered (tempered back to a certain hardness after a full hardening during heating and quenching).

Typically guns parts are nitrocarburized (Melonize/Tenifer etc) to provide a thin hard wear resistance layer of heat treat on the metal to resist scratches/damage and provide some corrosion resistance forming an FeNitride layer....at least my Smith is....

Hope this clears the air a bit

[dahermit]

Heat treatable steels are typically .30 and up carbon alloyed for hardenability depending on the section to harden deep (ie 4140, 4340). These are quench and tempered (tempered back to a certain hardness after a full hardening during heating and quenching).

You should perhaps mention that plain carbon steel (only carbon as a significant alloying element)with .40 carbon(medium carbon steel), cannot be heat treated significantly without sub-zero quench, then only become half-hard. The two steels you mention (4140, 4340) are not plain carbon steel, they are alloy steels. A plain carbon steel must have a minimum of .83% carbon(high carbon steel), to harden completely upon quenching.

[Only S&W and Me]

Depends on the steel section for plain carbon steels, but yes,generally do not have the hardenability to through harden. It's all about section and steel hardenability based on chemistry. Actually sometimes, depending on the product, you WANT a softer core and a harder surface to increase fatigue life, thus a fast quench of a plain carbon steel (ie 1030) in beneficial. All depend on what you need....

1040 can though harden if small or thin..(ie rod, plate). Water quench will be sufficient

Where did you get >.83 only can through harden...not true.

[dahermit]

Depends on the steel section for plain carbon steels,

Steel "section"? If you mean "thickness" of the part, heating in an oven ("soaking") for the prescribed time would negate any perceived problems with thickness.

but yes,generally do not have the hardenability to through harden. It's all about section and steel hardenability based on chemistry.

Wha...? In plain carbon steel (no other significant alloying elements besides carbon and iron), the amount of carbon determines if it can be hardened, unless you are talking about case hardening...then carbon is added to the outside.

Actually sometimes, depending on the product, you WANT a softer core and a harder surface to increase fatigue life,

"Case hardening."

thus a fast quench of a plain carbon steel (ie 1030) in beneficial. All depend on what you need....

1040 can though harden if small or thin..(ie rod, plate). Water quench will be sufficient

Here is a quote from "Machining Fundamentals", John R. Walker, The Goodheart-Willcox Company, Inc., South Holland, Illinois. page 377: "Carbon steel with less than 50 points [.50%] of carbon cannot be hardened."

Where did you get >.83 only can through harden...not true.

Plain carbon steel is made up of molecules that form in the shape of a cube with an atom of iron at each corner and an atom of carbon suspended in the center of the cube (body centered). This molecule is called ferrite. If the steel is heated to 1330 deg. F., the carbon atom is allowed to move. If there is more carbon available outside the ferrite molecule, five atoms carbon will take up position on the faces of the atom, and the one in the center will move to one of the faces (face centered). When this change has taken place and there are now six atoms of carbon and the original eight atoms of iron in each molecule, the molecule is now called, austinite. If that piece of metal is quickly quenched in water, the atoms cannot move out of the face centered arrangement (if allowed to cool slowly the molecule will revert to ferrite), and is under stress. This condition is now known as martinsite...it is hard steel (about 67 on the Rockwell C scale). Now if there is not enough carbon to form the austinite molecule, the martensite cannot be formed. Thus, low carbon steel cannot be hardened. However, if there are exactly 83 points of carbon (.83%), there is exactly the correct amount for hardening all the metal into martinsite. There is no way to case harden, inasmuch as if it is heated and quenched, all the metal hardens, and to case harden, it must be heated and quenched (Try to case harden a file(67 Rockwell C) and see what happens).
However, if the metal piece is hardened, and then drawn (tempered) some of the molecules will revert back to ferrite, giving up some of the hardness for toughness and will read lower on the Rockwell C scale.

[Only S&W and Me]

Dahermit....I could talk for days on this. I'm a full degreed Materials and Metallurgical Engineer who deals with this this stuff everyday for 25 years. This is basic 101 for me. You would not beleive the intense heat treat I get involved with daily. Yes, you can quench out steels with lower carbon and get some hardness. I've even done it with 1020. Thickness makes a big difference. Alloys and residual alloys will contribute. 1040 and up will quench out very nice in a small section. Just today got back from trip hardening 1065 fully in a small part section of .250". Go to SAE and read the hardenability curves (Jominy end quench test). This tells you how deep you can harden.Sometimes we fast quench 1040 in a larger section to "rim" harden and keep the core soft with no carburizing or case hardening.

I have to say, this John Walker (hope no relation) is seriously misleading/wrong in his writing...there are no molecules in steel (atomic lattice) and ferrite is not molecules and hardening not possible under .85, tempering causing ferrite etc etc etc.

[BobCat45]

<diffidence>
go to
http://www.dtic.mil/dtic/search/tr/
and search for monograph 88
one of the hits will be:
Title: Heat Treatment and Properties of Iron and Steel - download it.
Or go direct to http://handle.dtic.mil/100.2/ADA361141 and get it.

Also
http://steel.keytometals.com/default.aspx?ID=Articles

Get MIL handbook 5J at
http://femci.gsfc.nasa.gov/presentat...IL-HDBK-5J.zip
or http://www.everyspec.com/MIL-HDBK/MI...L_HDBK_5J_139/
and see Chapter 2

Info on the web:
http://www.crucibleservice.com/ and http://www.latrobesteel.com/technical_datasheets.cfm

http://www.msm.cam.ac.uk/phase-trans...ng/ecbain.html
- this is an absolute gem, but not one person in 500 will have the patience for it.

http://www.steelynx.net/
- you could drown if not careful.

</diffidence>

This is offered in the spirit of conciliation, and with the hope that some young person will be interested enough to consider a major in Metallurgy or Materials Science.

People were heat treating swords and other implements long before they had any fundamental knowledge of the processes, and getting excellent results. OTOH I know people who can write out all kinds of wonderful equations, who would be unable to turn an automotive leaf spring into a decent blade. We do best when we balance "book learnin'" with practical experience and knowledge.

Regards,
Andrew

[dahermit]

After reading the links provided in the above data sources, I have concluded that: 1) Some of what I have read in text books was in error. 2) Some of what I was taught in college was in error. 3) My memory has faded somewhat (I am 66). Therefore, one should consult the data sources as above as the definitive source of heat treat information.

[brickeyee]

The concern over the section size occurs since you can only cool the metal so fast through its surface.

A large section will not cool fast enough in the core, but will slowly cool down.

[BobCat45]

brickeyee,

That is exactly right. As Only S&W and Me said, it goes back to Jominy curves. Tip: many steel mills have little "gimme" booklets containing this kind of info. Contact your local rep and ask for one.

dahermit,

I turned 60 last winter and my memory is shot. I don't tell people anything anymore because:
1) I did not understand it perfectly when I first learned it.
2) If I don't use it often, I've forgotten even the little I knew.
3) I'm lazy - if I have to go look it up, I'll read it again so I understand it again, but still just tell where to look it up - people can read and get more from it than I can relate.
4) Once I start talking, I forget where I was going and wind up telling stories about my cats and the cute things they do - nobody wants to hear it.

To get back to reality (guns) - there was a guy in Houston, maybe 10-12 years ago, with a business called something like, Texas Longhorn Arms. He made replica Colt Peacemakers, out of the best-quality, cleanest 4340 he could get. It was 'way overkill, much better than "needed" and probably a bear to machine (very low sulfur) - but he wanted to be "the best" and, as far as I'm concerned, his guns were. My regret is that I was too cheap to buy one, and now he is either retired or passed on and there will be no more of them.

This does not prevent me from fantasizing about guns made from exotic, expensive alloys that would not rust/corrode in anything you would find loose on the Earth (i.e. hydrofluoric acid would take a toll on most nickel-based alloys, so would mixed hydrochloric / sulfuric). These would be overkill but still, real cool (in my opinion).

And I have to giggle when folks express doubts about the quality of the steel in some imported guns. Steelmaking has evolved to where modern steel is so much cleaner (less nonmetallic inclusions) and better, and the chemistry so much better controlled, than the very best steels of the 1940s-1950s that it is amazing. If their QA / process-control people are awake, there is no reason offshore steel should be at all inferior to our best from the golden era (i.e. when the 1911 was new, and the Garand was about to be adopted).

Anyway, time for me to shut up and go back to whatever I was doing... have fun!

[dahermit]

And I have to giggle when folks express doubts about the quality of the steel in some imported guns. Steelmaking has evolved to where modern steel is so much cleaner (less nonmetallic inclusions) and better, and the chemistry so much better controlled, than the very best steels of the 1940s-1950s that it is amazing. If their QA / process-control people are awake, there is no reason offshore steel should be at all inferior to our best from the golden era (i.e. when the 1911 was new, and the Garand was about to be adopted).

Do you mean that the steel used to build the Titanic was not high quality???!!!

[BobCat45]

<cackle> if I can believe what I read on the Internet, that stuff was poor even for its time... and the rivets were worse.

Somebody has a .sig line that says something like, "the Titanic was built by professionals, the Ark was built by an amateur."

Oh - and I looked up Texas Longhorn arms, and I was wrong - it was not 4340, it was 4140. Should have looked before I babbled.

And - was Sam Colt left handed? Apparently the Texas Longhorn guy thought so, because the loading gate on the SAA is on the right side, so you have to change hands to load and unload it. His pistols were mirror images of the Colt - you could keep the revolver in your right hand, operate the loading gate and ejector with your left, and never loose your grip on the grip while reloading. That sounds cool!

Regards,
Andrew

[grymster2007]

4340 is a bit harder and higher in tensile strength, but both it and 4140 are easily machined and make for excellent gun parts. I thought I'd make my conversion cylinder from 4340. Probably not necessary, but building something just a little better than it needs to be is kinda fun.

[BobCat45]

That is because you know how. Someone used to cutting 12L14 all day, and getting paid by the piece-part, would not be so calm about it.

Yes - making it "better than it needs to be" is fun! It drives the Supply Chain people crazy, but when the part is for your project, and you are on your own time, better is better.

http://handle.dtic.mil/100.2/ADA076035 - or Google WADC TECHNICAL REPORT 52-73 and get the .PDF - if you want a good belly laugh. It is from 1952, and describes 4330V - about twice the impact toughness of 4340 when both are heat treated to the same strength. We are seeing it come on-line in the oilfield business now, only about half a century after than the fly-guys got it, but better late than never. I think it would be wizard stuff for barrels and receivers, but only if you are making it for yourself - never get it past the people who know the price of everything and the value of nothing.

Regards,
Andrew