What is heat treating an action?

[ascast]

[SIZE=3]Just for discussion[ - what is actually being done when an receiver is heat treated? Is this commonly done while case hardening; at the same time. I understand that it is to relieve internal stress from forming or imparted during machining. Also to change the metal structure at the molecular level somewhat. Case hardening is to harden the outer surface by heating so that it absorbs carbon. The flip side question is- what happens when a receiver goes through a house fire? And furthermore, an action for a 1800's black powder rifle should probably not require as much consideration as a modern high power rifle. just wondering, I keep finding old actions that went through fires./SIZE]

[john.k]

Its quite a complex subject...I recall at one time gearbox gears were being toughened by freezing in liquid gas .......I think it was the New Process box used in Dodge small trucks.

[414gates]

The process of annealing is to hold metal at a fixed temperature for a long enough time for the crystal structure to re-grow. Annealing is a softening process for metals, when the crystals re-grow, they are no longer under any stress or strain.

1. annealing of steel is at 1500 F
2. a typical house fire reaches 1100 F

Assuming the receiver is steel, a house fire won't soften it up.

Case hardening is a different process altogether, and is done after annealing.

All steels can be annealed, not all steels can be case hardened.

[uscra112]

1. annealing of steel is at 1500 F
2. a typical house fire reaches 1100 F

Assuming the receiver is steel, a house fire won't soften it up.

Case hardening is a different process altogether, and is done after annealing.

All steels can be annealed, not all steels can be case hardened.

Not true. 1100F will definitely draw the temper of hardened steel in just a few minutes. Small parts like triggers and sears are especially vulnerable.

This isn't a simple subject. There are engineers whose entire career centers on how steels are heat treated, to the exclusion of all else. They tend to have advanced degrees in Chemistry.

Buy and read repeatedly:
https://www.amazon.com/Heat-Treatment-Steel-Comprehensive-Casehardening-Heat-Treating/dp/1375773216/ref=sr_1_3?crid=1V0L2AONC6HA6&keywords=heat+treating+steel&qid=1654078100&sprefix=heat+treating+steel%2Caps%2C1920&sr=8-3

Or if you want to spend the money for the Masters Degree course:

https://www.amazon.com/ASM-Handbook-Treating-Fundamentals-Process/dp/1627080112/ref=sr_1_6?crid=1V0L2AONC6HA6&keywords=heat+treating+steel&qid=1654078100&sprefix=heat+treating+steel%2Caps%2C1920&sr=8-6

[414gates]

Not true. 1100F will definitely draw the temper of hardened steel in just a few minutes.

Temper and anneal differ are different processes, one does not replace the other, although the results are confused with each other.

A temper is a stress relief, which depending on the steel can start at 500 F.

The general opinion is that when you apply heat to metal, you anneal it. It is incorrect. An anneal is a very specific operation, it is time specific and temperature specific. Time is very important because metal crystals don't grow instantly.

This idea of heat being an anneal is carried forward from the heating of brass case necks, which is incorrectly called annealing. it is not annealing, it is stress relief.

[uscra112]

Tempering is not stress relieving.

[beechbum444]

This topic gets me thinking every time a I a rifle or action on an auction site that has been in a house or cabin fire

[414gates]

Tempering is not stress relieving.

https://www.britannica.com/technology/tempering-metallurgy

"The process has the effect of toughening by lessening brittleness and reducing internal stresses."

[Scrounge]

Not true. 1100F will definitely draw the temper of hardened steel in just a few minutes. Small parts like triggers and sears are especially vulnerable.

This isn't a simple subject. There are engineers whose entire career centers on how steels are heat treated, to the exclusion of all else. They tend to have advanced degrees in Chemistry.

Buy and read repeatedly:
https://www.amazon.com/Heat-Treatment-Steel-Comprehensive-Casehardening-Heat-Treating/dp/1375773216/ref=sr_1_3?crid=1V0L2AONC6HA6&keywords=heat+treating+steel&qid=1654078100&sprefix=heat+treating+steel%2Caps%2C1920&sr=8-3

Or if you want to spend the money for the Masters Degree course:

https://www.amazon.com/ASM-Handbook-Treating-Fundamentals-Process/dp/1627080112/ref=sr_1_6?crid=1V0L2AONC6HA6&keywords=heat+treating+steel&qid=1654078100&sprefix=heat+treating+steel%2Caps%2C1920&sr=8-6

The problem with your first reference is that it is around 100 years old. There has been a LOT of water under that bridge. If you're making parts for an old boys rifle, it's a great reference! if you're working with modern alloys, not so much, so you need more modern references. Your second reference is probably available at your local library in the Reference section, but you can get a lot of the info there from these folks: https://archive.org/search.php?query=hardening+and+tempering&page=3 Down the page a bit is the Workshop Practice Series book #1, Hardening, Tempering, and Heat Treatment for Model Engineers. It's only 30 or 40 years out of date, and written for British model engineers, but is a good treatment of the subject for amateurs. I doubt it mentions cryo treatments, though they've been around for a while, but I'm too lazy to look at my paper copy. Good thing about Archive.org is that most of what they have is readily downloadable in multiple formats. I've got gigabytes of stuff from them. They have several collections and the one I like the most is probably the https://archive.org/details/folkscanomy Library of Books. There are subsections on Defense, and Engineering that I've ravaged pretty thoroughly, but also look at the Public Library of India, and the American and Canadian libraries. Some of the newer books are only available to borrow, and that hasn't worked well for me.

[Scrounge]

Temper and anneal differ are different processes, one does not replace the other, although the results are confused with each other.

A temper is a stress relief, which depending on the steel can start at 500 F.

The general opinion is that when you apply heat to metal, you anneal it. It is incorrect. An anneal is a very specific operation, it is time specific and temperature specific. Time is very important because metal crystals don't grow instantly.


This idea of heat being an anneal is carried forward from the heating of brass case necks, which is incorrectly called annealing. it is not annealing, it is stress relief.

Also depends on which metal you're talking about. You anneal copper (and copper alloys) by getting it red hot and quenching in water. Higher carbon steels will harden if you do that to them, and depending on the alloy may well crack. Tempering is adjusting the hardness of steel, not stress relieving it. It's done after quenching, to get the hardness where you want it. If you do not temper, you risk shattering the steel, as it can get glass hard.

Case hardening is increasing the carbon content of a thin layer of of the iron surface, and hardening that. That thin layer is the "case." The core remains whatever it was, and done to mild steel, it leaves a soft core with a hard case on the outside. It's used for adding wear resistance, and decoration as in color case hardening, while retaining a softer and less brittle core. See any of the books recommended above, not just the ones I mentioned.

[Der Gebirgsjager]

Speaking as a gunsmith (Ret.) only, not having a degree in a metallurgic science, I can only tell you that in the real, practical world it is a case by case basis as to whether or not a gunsmith will work on an action that's been through a fire. The feeling is that if the action was heated for a protracted period it may have "drawn" to the point of being dangerously soft, and if it was subjected to extreme heat it may have changed its carbon content and become brittle.

I did work on restoring and refinishing two pre-WW II Win. Mod. 70s that belonged to a neighbor. The stocks were charred, but salvageable, and the metal showed no discoloration. They had belonged to his dad who had them secreted between the folds of a mattress stored in the garage. When the house caught fire the mattress was burning but not fully engulfed in flames, and the fire dept. hosed it down with water, which probably did more damage than the fire as they were thoroughly rusted.

But when someone presents you with a rifle or handgun that has had the wooden stock or grips completely burned off, you can pretty well bet that it got pretty hot! A gunsmith will want to know the entire story in as much detail as possible as pertains to where the guns were in the fire and how long, and bearing liability issues in mind will usually refuse to work on them. Heat treating is a more or less exacting science, and the temperature and for how long is well known for most gun steels. Gunsmiths routinely harden small parts that they make in their shops, and draw the hardness back as needed to avoid brittleness, but when the gun has been through a fire the equation changes, and it's usually wise to avoid working on them.

DG

[Scrounge]

Speaking as a gunsmith (Ret.) only, not having a degree in a metallurgic science, I can only tell you that in the real, practical world it is a case by case basis as to whether or not a gunsmith will work on an action that's been through a fire. The feeling is that if the action was heated for a protracted period it may have "drawn" to the point of being dangerously soft, and if it was subjected to extreme heat it may have changed its carbon content and become brittle.

I did work on restoring and refinishing two pre-WW II Win. Mod. 70s that belonged to a neighbor. The stocks were charred, but salvageable, and the metal showed no discoloration. They had belonged to his dad who had them secreted between the folds of a mattress stored in the garage. When the house caught fire the mattress was burning but not fully engulfed in flames, and the fire dept. hosed it down with water, which probably did more damage than the fire as they were thoroughly rusted.

But when someone presents you with a rifle or handgun that has had the wooden stock or grips completely burned off, you can pretty well bet that it got pretty hot! A gunsmith will want to know the entire story in as much detail as possible as pertains to where the guns were in the fire and how long, and bearing liability issues in mind will usually refuse to work on them. Heat treating is a more or less exacting science, and the temperature and for how long is well known for most gun steels. Gunsmiths routinely harden small parts that they make in their shops, and draw the hardness back as needed to avoid brittleness, but when the gun has been through a fire the equation changes, and it's usually wise to avoid working on them.

DG

I sure won't argue with you on that! I'd lost track of the OP's interest in firearms that had been burnt. On an original 1800's gun it might not matter at all, since the steel was likely pretty soft to start with, but I'm a ham-handed, thumb-fingered amateur, not a gunsmith. I do keep thinking of a GSO in my collection that I bought in Turkey, when I lived there. It has what I think is an authentic antique flintlock, but the "barrel" is a piece of water pipe filed to resemble a gun barrel. There is no breechblock, either. I've considered building a barrel for it, as the stock and lock are beautifully made, but I think it would need to be 36 caliber at most for the size of the barrel channel. A .22 caliber barrel might be better still! ;)

Bill

[M-Tecs]

Some good info on this thread and some not so much.

As stated this can become a very complex and detailed issue depending on application and materials.

That being said generalizations can be used too provide a fairly accurate overview for firearm applications.

There are two basic groups of ferrous based metals in regards to heat treatment and heat treatment is different depending on carbon content. Low carbon steels are steels like 1020 or 8620 that lack enough carbon to be hardened through heat treatment without the addition of more carbon. That process is referred to as case hardening. During this process various methods are used to increase the surface carbon content. Depending on the process and time this may be only a .001" or .002" deep or much deeper. I have seen case a deep as 3/16" on gears.

With medium or high carbon steels no addition carbon is required and hardness is generally all the way through the material not just on the surface like case hardening. The material temperature is raised until the material become none magnetic. A magnet is used in torch or forge heat treating. More sophisticated methods use ovens and temperature charts and sensors. Once the material has reached temperature and stabilized it is quenched. Quenching medium could be water, oil or air depending on material. At this point the material is full hard and may be to brittle for some applications so the next step is tempering.

Tempering occurs after HT. It is nothing more than raising the material to a specific temperature or color to provide the proper balance of hardness verse toughness for the specific application. With some steels that can be as low as 400 degrees Fahrenheit.

Annealing/normalizing is process that has various meaning for various application. For the ferrous HT process is generally means heating and slowly cooling to get the material to it's softest stress free condition possible. While annealing/normalizing may be used in the manufacturing processed in firearms it has little application for firearms users/gunsmiths outside of manufacturing processes. Brass is a different application and annealing necks has a great benefit.

As to firearms in a house fire that is case by case. Some older firearms are low carbon and not affected. Most modern firearms do have some form of HT and a house fire can affect them. Rule of thumb is if the wood is burnt off and or the spring are soft the firearm needs to be reheat treated. If the metal has scale on it needs to be HT'ed or junked There are only a couple of companies that still do this the last time I checked.

Some basics here:

https://learnmechanical.com/heat-treatment/

https://www.machinemfg.com/heat-treatment-processes/

https://pediaa.com/difference-between-annealing-hardening-and-tempering/

[uscra112]

@scrounge: Only guns I know of that can certainly survive a fire are cheap 19th century relics like the Stevens 44s I collect. No high carbon steel in them at all, except for springs. Receivers are malleable iron. Everything case hardened. (And they stayed that way right up to WW2, too! Never were brought into the 20th century.)

[Mal Paso]

I had 1 1/8" jackhammer steels that went through a house fire. They looked OK but did not survive first use. The shank broke off and the end had peened so badly the hammer had to be disassembled to remove it.

[john.k]

It often claimed that if springs are still springy,then the gun is OK.....This doesnt take account of the hardened contact surfaces in the trigger and firing mechanism,and these surfaces fail quickly from deformation if softened........parts like a barrel are often tempered at 600DegC ,and can be OK after much higher heat than collapses springs.

[James Wisner]

Guns that have been thru a fire, that is a WIDE variation of damage

In the past 52 years I have been Gunsmithing I have seen the good and the BAD

One fire the rifles were stacked up in a corner, so when the roof came down it protected most of the rifles.
The barrels were bent and useless, the front half of the forearms were burnt to a crisp, even the front scope bells were melted.
The actions were not damaged
One was a Savage 99, the work was to replace the barrel, a new forearm, a new scope, reblue the metal, refinish the butt stock and it went back to the customer.

Bad ones.
Any time you see scale on the metal, do not bother with it.

They figure that carbon migrates into the steel at .008" per inch at 1500 DF, this is from the flip side when you are Case Hardening

I have seen many guns with .015" scale on the metal.
I also understand that with all the free HOT carbon in a fire zone you can get a rough idea of what is going on with the metal when the fire is that hot at that time.
By the time you get the scale off you have lost most of the fitting required between the parts, plus depending on the metal it will have to be Carbon Restored, Quenched and Tempered, if an alloy.
Or Case Hardened, and Tempered if it is a mild steel

Example a Remington M700 receiver is made from pre-hard 4140 which is about 38 - 40 RC, the bolt will be roughly 5 RC points harder

While a Winchester 1892 or 1894 receiver built before WW1 would have been made from roughly 1025 - 1030 steel and would be about 28 - 32 RC in hardness

My 2 cents worth
Jim Wisner

[uscra112]

Rem 700 receivers were made from prehard? I knew they were made from tube, but that fact has somehow escaped me.

[bigdog454]

What m-tec rote id good info. I worked in a tool and die shop for years, and one of my duties was the heat treatment of the dies that needed so. to heat treat a metal you need to know the alloy of it. You get that from the metals vendor or metals foundry. I have an engineering degree and was certified to do heat treating, I would not attempt to heat treat an action without a lab result first.

[john.k]

heat treaters would often get the gearset out of a truck axle to reharden......these attempts would inevitably leave the customer $1k out of pocket after the heat treat and new bearings for the diff.........the gears would fail in under five thousand miles.........I once bought a excavator gearset from a burnt machine.......was the only one available on the planet......I warned the owner to trade the machine ,..... once it was going ,he assumed it was good........not so,whole gearset failed again within six months ,exactly as I had said........burnt set cost $10k,he had to go new ex Korea for an uprated assembly ,cost $60k plus fitting..........the excavator was a Samsung ,and worth maybe $50k to a newbie or a farmer.

[M-Tecs]

heat treaters would often get the gearset out of a truck axle to reharden......these attempts would inevitably leave the customer $1k out of pocket after the heat treat and new bearings for the diff.........the gears would fail in under five thousand miles.........I once bought a excavator gearset from a burnt machine.......was the only one available on the planet......I warned the owner to trade the machine ,..... once it was going ,he assumed it was good........not so,whole gearset failed again within six months ,exactly as I had said........burnt set cost $10k,he had to go new ex Korea for an uprated assembly ,cost $60k plus fitting..........the excavator was a Samsung ,and worth maybe $50k to a newbie or a farmer.

That would be from the heat treaters not using the correct process. Medium and high carbon steels can be damage by too high of temperatures and or too long of soak times. Once the carbon is burnt out the part is basically scrap. Most larger gears are case hardened and respond well to re-case hardening even if the case hardened layer is worn off or had the carbon burnt out. As simple heat and quench without inducing carbon does very little to nothing.

some interesting reading here

https://gearsolutions.com/features/heat-treating-heavy-duty-gears/

https://gearsolutions.com/features/heat-treatment-of-gears/

[uscra112]

Medium and high carbon steels can be damage by too high of temperatures and or too long of soak times. Once the carbon is burnt out the part is basically scrap.

As witness the infamous story of the low s/n Springfield 1903 receivers.

[M-Tecs]

As witness the infamous story of the low s/n Springfield 1903 receivers.

There are still differing views on this issue. The early pre-nickel steel 1903 were case hardened.

http://m1903.com/03rcvrfail/ Too long to post but somewhat a different take than Hatchers had.

https://www.tapatalk.com/groups/collectorguns35625/a-question-about-springfield-1903-receivers-t2622.html

The subject is discussed and cussed frequently; it is always contentious enough to provoke some heated and emotional debate.
The Army considered taking the "low numbers" out of service, and even generated a few policy documents to that effect, but the policy appears to have been largely ignored. The sea services (USN, USMC, USCG) had no such policy and kept their low numbered rifles in service until they were replaced by more modern rifles.
Sometime in the late 1950's, an NRA member wrote in to "Dope Bag" and asked pretty much the same question you did. This is the response, quoted in its entirety:
"I have been told of low numbered Springfield rifles which may be dangerous, though the reason is not clear. What is the fact on this matter? ~ A.R.A.
Answer: Before World War I, Model 1903 rifles manufactured at Springfield Armory and Rock Island Arsenal were made of carbon manganese steel, casehardened. A few of these rifles in service suffered burst receivers or broken bolts from high pressure or other abuse.
In 1918 the heat treatment was changed at both Springfield and Rock Island and this greatly strengthened the receiver and bolt. The new double heat treatment went into effect at about rifle No. 800,000 at Springfield and at about No. 285,507 at Rock Island. It is practically impossible to burst a receiver or break a bolt of rifles with serial numbers above those, though with soft cartridge heads or dangerous pressures failure of the cartridge case can permit enough gas escape to splinter the stock or bulge the magazine and endanger the eyesight of a shooter not wearing shooting glasses.
At No. 1,275,767 Springfield Armory changed the material in the bolt and receiver to nickel steel. At No. 319,921 Rock Island began using nickel steel for some of its receivers but continued with the improved heat-treated carbon manganese steel for others. The nickel steel receivers were marked NS on the front face but this mark is covered by assembling the barrel to the receiver and the only way to tell the difference is by a file test. The carbon steel receivers are hard on the surface and can scarcely be filed at all, but the nickel steel receivers are fairly soft on the surface and the file will take hold. Nickel steel receivers and bolts are very nearly as strong as the double heat treated ones. The double heat treated receives and bolts are considered somewhat the more desirable, because their hard surfaces allows easiest bolt manipulation.
During World War II, M1903 and M1903A3 rifles with serial numbers over 3,000,001 were made by Remington Arms Co., Inc. and L.C. Smith & Corona Typewriter Co. Their receivers and bolts were made of high strength steels, and all these are considered high number rifles.
As to safety, there were about 800,000 low number M1903 Springfields and 285,000 Rock Islands made, or over a million in all, and they were continued in service until superseded by the M1 rifle. From 1917 to 1929 inclusive, records were kept of all accidents to receivers of Springfield rifles, and during that time of the 800,000 low-numbered Springfields there were 33 reported as burst or about 1 in 24,000. Of the 285,000 Rock Island receivers there were 24 reported burst or about 1 in 11,800. There 9 cases of severe injuries; no one was killed, and in most cases the there were no injuries or only minor ones. From the above, the user of one of these rifles can judge whether or not he cares to continue firing it. The chance of an accident does exist although it is slight.
During all those years there was no reported case of any receiver burst or bolt broken in any rifles having serial numbers higher than Springfield 800,000 or Rock Island 285,507. [Ed Note: This is not true. There is at least one case reported in Hatchers Notebook of a Springfield receiver numbered above 800,000 that burst when a 7.92 x 57 mm cartridge was fired in it. RLS]
Springfield Armory investigated reheat treating low-numbered receivers and officially reported that reheat treating them would not guarantee safety. This was because failures were generally due to burnt steel from overheating while forging, and burnt steel cannot be restored by any known method short of remelting. ~ J.S.H."

[lar45]

Heat treating is a rather large and complex subject.
I'll try to cover a small amount from the knife making, or small gun parts point of view. This should not be applied to the action!
If the heat treatment of an action is not done correctly it can kill you.

Here is a TTT Diagram for Eutectoid steel.
301185

https://materials-today.com/ttt-diagram-of-steel/

If you take a piece of simple high carbon steel such as 1080 or 1095, and heat it up high enough the grain structure will turn into Austenite, this is generally a little bit above where the steel will not be attracted by a magnet. For specific temperatures and times, look at the chart for the steel you are working with.
On the chart, you will see a big sideways curve, this is the Pearolitic nose.
From Austenite you can change the grain structures and properties of the steel into several states depending on how fast or slow you cool the steel, or if you cool and hold at a specific point.
To make a knife or hard gun part, you heat to Austenite, then cool the piece fast enough to beat the pearalitic nose of the curve.
Saltwater cools faster than water, water cools faster than oil...
If you cool fast enough the steel transforms into Martensite. The grain structure is very small with sharp corners. This is very strong, hard and can be brittle. To get rid of the brittleness while still keeping most of the strength and hardness, you need to heat it up some and "Temper" it. Heating will start to round off the corners of the grains, this will increase flexibility and decrease hardness and strength just a little bit. The longer you heat it, the rounder the corners will get. Heat it long enough and the grain size will start to grow.

From a knifemakers point of view, take a piece of 1095, heat to Austenite, quench in water and break it. Clamp it in a vise and bend it with a crescent wrench. You will have a very hard and brittle piece of steel with a very fine grain structure.
Now do the same heat and quench with a second piece of 1095. This time we are going to temper it. Place in a 400F oven for an hour. Then bend it. It should flex more than the first piece, then break if you lean on it hard enough. Heat it for another hour and it will flex even more, but you only loose a little bit of hardness and strength. You now have "Tempered Martensite ". This is a good thing for a knife or small gun parts.

I saw part of a barrel from an 03A3 that had been heated to take the front sight off, then quenched in water. When it was shot, it fractured and blew the end of the barrel off.

Sorry if I rambled a little, I got distracted a couple of times...

[John Taylor]

With most fire damaged guns I look at the springs. If the spring no longer has tension or has lost form the gun got hot enough to effect the heat treat, usually 700 to 800 degrees. On the 1903 Springfield I read someplace that they did not have a temperature controlled oven until about 800,000. Going by the color for heat treat the guys during the day would not see red as early as the guys at night. So the actions quenched during the day were a lot hotter than the ones quenched at night. I don't know how true this is but I found out while heat treating small parts that if the quench water is cold the part can become more brittle and sometimes split or brake. I use oil for quenching springs which helps a bunch.

[lar45]

I was making a pry bar out of a potato digger chain link years ago. I got it hammered out, bent just right and ground perfect. I then heated to red and water quenched. I tapped it on the anvil to hear it ring and it shattered like glass. I made another, quenched in oil this time and it's been working great for 20 years.
This was all before I went through engineering school and took some metallurgy classes...

[uscra112]

John,. that story comes right out of Hatcher's notebook.

[john.k]

A common trick was to quench in water with 1/8" layer of oil on top..this gives a tough quench without filling the shop with smoke.

[john.k]

The local heat treaters used to have a big sign up at the front counter "Satisfaction NOT Guaranteed."..........they were con artists too,and would never say when something was bound to fail........I once took the endplates from a big hydraulic motor to be 24hr nitrided.........on picking them up , a woman grabbed me outside ..."We had that same part nitrided last week,and the big part didnt harden,only the small part".....so they could have said that wont work on the 200lb part......but they charge nitriding by the pound.

[M-Tecs]

A common trick was to quench in water with 1/8" layer of oil on top..this gives a tough quench without filling the shop with smoke.

Why the oil if it's a water hardening steel? If it's an oil hardening steel the 1/8" of oil will do nothing and the quenching will be way too rapid for oil hardening only steels.

I've never used this method personally but I do have some knife making friends that tried this method using 2 inches of oil on the surface. They weren't overly impressed and gave up on it. That was shortly after they read about it here:

https://www.bladeforums.com/threads/oil-over-water-quench.589042/

On the industrial side they take great pains to keep water out of the oil. The quench tanks are generally heated to specific temperature for specific materials. Even the type of oil determines the results. HT's oils have specific quench rates from fast to slow. In certified HT shops the quench oil normally is heated between 120 degrees & 160 degrees depending on material. I mostly kept my quench tank at 120 degrees.

Some examples of what's available here:https://forgingworld.com/what-is-the-best-quenching-oil/

Some water in oil issue here:

https://www.houghtonintl.com/sites/default/files/resources/article_-_care_and_maintenance_of_quench_oils.pdf

https://www.houghtonintl.com/sites/default/files/resources/water_removal.pdf

https://gearsolutions.com/departments/hot-seat/water-in-oil-based-quenchants-can-be-problematic/

https://www.globalspec.com/learnmore/materials_chemicals_adhesives/industrial_oils_fluids/quenching_oils_heat_treatment_fluids

https://www.machinerylubrication.com/Read/430/quench-oils#:~:text=One%20of%20the%20oldest%20tests%20to% 20quantify%20the,%28Figure%203%29.%20Figure%203.%2 0GM%20Quenchometer%20Test%20Apparatus

[todd9.3x57]

what it comes down too, is whether you trust the true gunsmith (not a shade tree gunsmith either, hey wait a minute, i am a shade tree gunsmith:redneck:) or do you trust google?

i'll trust the true gunsmith. i don't trust Wikipedia or google.

[M-Tecs]

what it comes down too, is whether you trust the true gunsmith (not a shade tree gunsmith either, hey wait a minute, i am a shade tree gunsmith:redneck:) or do you trust google?

i'll trust the true gunsmith. i don't trust Wikipedia or google.

None of the people (true gunsmith whatever that is) or sources you listed what would be termed as subject matter experts on heat treating. There are exceptions like Doug Turnbull, Bobby Tyler and a couple of other "gunsmiths" that I would trust. I would be willing to bet 99% of the gunsmiths only know enough machining and or heat treating to just get by if that. I trusted certified heat treaters that adhere to AMS or SAE standards.

Heat treating started as an magic followed by art. Today it is 100% science and 100% repeatable and predictable. Until Clinton/Gore eliminate the mil. spec. standards the information was cheaply and readily available. That info is now controlled and sold by either the SAE or AMS. The info is no longer readily available or cheap anymore.

The USAF/NAVAIR Technical Order 1-1A-9 is still available and good reference https://www.robins.af.mil/Portals/59/documents/technicalorders/1-1A-9.pdf?ver=2017-05-03-094319-467

Certified Heat Treaters will adhere to the SAE AMS2750 to ensure their equipment is properly calibrated.

Firearms are very old technology normally designed with significant safety margins made out of material that are fairly tolerant of marginal heat treat processes. History is filled with HT mistakes that lead to catastrophic failures.

[JackQuest]

Tempering is not stress relieving.

Agreed; tempering is not stress relieving. It is actually inducing a certain level of stress based on alloy, highest temperature reached during heating, quench temperature, quenching fluid (water, various oils, et.cet.) and quench duration (overall cool down).

Also, annealing does not remove all stress. The size and placement of alloying elements (chrome, nickel, vanadium to name a few) create interstitial defects in the crystal structure of the overall metal object. These usually toughen the metal against the movement of cracks in the overall alloy.

As noted above, heat treatment, tempering and annealing are all different but related to each other. To throw a wrench into everything, there is also the Fermi temperature of the alloy. This is the point where the metal loses any ferro-magnetic properties (being attracted to magnet). LAR45 speaks to this above. If you watch the guys making knifes on TV you see them test the heated steel with a magnet to make sure they are above the Fermi temperature before quenching. The gasps of horror come when the knife maker quenches in water and not oil.

[Scrounge]

@scrounge: Only guns I know of that can certainly survive a fire are cheap 19th century relics like the Stevens 44s I collect. No high carbon steel in them at all, except for springs. Receivers are malleable iron. Everything case hardened. (And they stayed that way right up to WW2, too! Never were brought into the 20th century.)

IIRC, my "collection" of rifles numbers 6, three of which are Stevens boys rifles. I have one early model Favorite that I believe is an 1884 or thereabouts, in .22LR, a 1915 Favorite in .32 RF Long, and a #26 Crackshot in .32 RF. Those, and the 1903A3 National Ordinance action frankengun are the only ones I'll be doing any "gunsmithing" on. Do not intend to mess with heat treating or case hardening. Don't know how it shipped, but the .22LR Favorite my dad bough when he was a young teen, broken, and he bubbaed it to work well enough that all the older 6 of my brothers and sisters learned to shoot with that rifle is all white metal now, and has been as long as I've been using it. Call it maybe 63 years... I've replaced a couple of screws, and will be fitting a new extractor one of these days, but keeping all the bubbaed parts for the history. The two youngest sisters didn't ever get to shoot it, as (I learned a couple of years ago) the screw for the lever that dad brazed a head and hand filed to shape stretched enough to no longer lock up the action. We thought it was shot out for 20 or 30 years. Nope, not yet. The other two are project rifles I bought from another member here. I need to card the rusted actions, and then steam them to see if I can get some blue on them, make CF breach blocks for them, and finish forming up some brass I've bought. Will also be making dies and such to keep reloading for them, and re-make more brass, and I won't be disposing of the original RF blocks. I'd say "cheap 19th century and earlier relics..." The rifles Jonathan Browning was making in the 1830's were made in his blacksmith's shop of, probably mild steel at best, and if I ever managed to lay hands on one, I wouldn't muck about with it at all, but anything similar and unmarked might be fair game for my practice pieces. I will never be a real gunsmith. But I'm happy tinkering with low value weapons.

[uscra112]

The first Favorites were the "sideplate" models, produced in 1892 and 1893. Then came the "1894" model with the one-piece receiver, which was made almost unchanged until 1915.

Stevens receivers were always made of malleable iron. Not heat treatable in the sense that steel is, and they still contain enough carbon thaT they can't be fusion welded, because the carbon goes back into solution making the metal very brittle. Repairs have to be brazed.

[john.k]

Malleable iron wont be hurt strengthwise if it isnt melted .............the modern equivalent of malleable is SG or Ductile iron......same result by a cheaper process......some years ago there was a craze among heavy equiptment manufacturers to make big parts of ductile iron.......for instance Case made front axles ,loader parts,and main backhoe pivot castings.......if these parts had a breakage ,you had to buy a new replacement.......even Caterpillar got caught up in the craze....but the big buyers of fleets wernt happy at high maintenance costs caused by non repairable parts.

[uscra112]

I just took possession of mu latest Gunbroker folly, an early 1915 Favorite that Bubba had "color cased" with a welding torch. Sometimes called "fire blued". As noted above, it won't have hurt the receiver any. It'll stay that way until after I have it rebuilt. If the gun shoots, I may have it color cased for real, even though 1915s never were.

[Geezer in NH]

Colorcase by watercolors was a course offered on the Double Gun Jornal by Oskar Gaddy at one time more than a decade ago as a JOKE.

99.9% of firearms in a house fire where the wood was burned off are scrap. My shop did fire restoration the fire atmosphere damaged guns. Best that can be done is bead blast and re-blue, if the springs were not springs the gun is scrapped. Pushing it is not worth the cost. Sorry