Jimro and Dipper ? Heating steel.

[Hello123]

I am a little nervous I may have screwed something up. I glued with Devcon one of my action screws to the bottom metal while bedding my bolt action rifle.

I eventually had to drill out the screw head to remove the gun from the stock. In the process of trying to get that booger of a screw out I used a propane torch to try to make the devcon brittle.

My concern is that I may have screwed up the steel by the heat transfer from the screw to the rifle action. I didn't see the metal turn colors. Is this a legit concern?

[dipper]

I don't think it is much of a concern.
If I understand correctly, you heated the head of the action screw up with your propane torch while the barreled action was still in the stock...it wouldn't break free so you drilled the head of the screw out to remove the barreled action.
I think it would be virtually impossible to do any damage to your action using a propane torch to heat the head of an action screw.....don't think you could even approach the temperatures needed to affect the action even if you held the torch on the screw for sometime.
The bottom metal, stock and barreled action itself would act like a big heat sink and you would have to hold a propane torch on it for I don't know how long to even approach a temperature that would affect the heat treatment of the action.
Next time, wax the action screws and apply a coat of grease to the screws and floor plate and the bedding material won't stick the parts together.

[Hello123]

Thanks dipper, that makes me feel a lot better. The assessment of the situation is correct. I had enough release agent everywhere except the action screw. Live and learn. Thanks for responding.

[Jimro]

Odds are your action is fine. The oxidation color changes aren't necessarily the best indicator of whether the temper was affected, but it at least gives you peace of mind that you didn't reach oxidation temperature.

What kills an action temper is heat and time, so low heat for a long time can do as much damage as much higher heat for a much lower time period. But from what you describe I wouldn't be too concerned, as you had minimal heat for minimal time with no oxidation.

Sorry I've been out of the loop, Uncle Sam has me in the middle of the desert, and internet access is "spotty".

Jimro

[Hello123]

keep up the good work Jimro, we are rooting for you!

[HisSoldier]

low heat for a long time can do as much damage as much higher heat for a much lower time period.

That's the first I've heard of that, no offense but I think that would need a bit of qualification. My understanding is that any changes occur at a certain temperature and time doesn't effect the changes, that is, 375 degrees held for ten years will effect the temper as much and no more than 375 degrees for five minutes. If I'm wrong my whole understanding of heat treatment is going to have to be reexamined.

Thank you sir for your service. May God bless the troops!

[dipper]

HisSoldier, you are correct.

The metal would not change unless it was exposed to temperatures GREATER than the original draw temperature.
If a metal has a draw ( or temper if you like) temperature of 400 degrees, and that is what it was tempered at, you could put it in a furnace at 300 degrees for days and it would not affect the metal.
Go over 400 degrees, and you run into problems.

[brickeyee]

My understanding is that any changes occur at a certain temperature and time doesn't effect the changes, that is, 375 degrees held for ten years will effect the temper as much and no more than 375 degrees for five minutes. If I'm wrong my whole understanding of heat treatment is going to have to be reexamined.

The issue is heat penetration.
You can only measure the temperature at the surface, and need to allow enough time for the cross section to reach a uniform temperature unless you are trying to do only surface changes.

The soak time required for heat treating processes is a function of cross section, and if you can apply a higher temperature without overheating the surface before the core comes up to the desired temperature.

[HisSoldier]

I assumed core temperature was the criteria.

[brickeyee]

But you cannot measure core temperature, and in the interest of speed the oven temp is set higher than is needed at the core.

In well done heat treating the oven is set only slightly above the desired core, and then the job takes time.
Sometimes a lot of time.
Guns are relatively small cross section items, so you do not need a huge dwell.
The closer the oven is set to the actual desired temperature the longer the dwell required to ensure a uniform temperature is reached throughout the metal.

In a full production environment a test piece(s) is manufactured, drilled for thermocouples, and then the heat treat schedule determined.

[HisSoldier]

But you cannot measure core temperature, and in the interest of speed the oven temp is set higher than is needed at the core.

I was addressing something entirely different, the notion that long term at temperature tempers more than short term at temperature. Perhaps that was was was meant, time to reach temperature.