Does tempering need to be done after case color hardening?

[juanvaldez]

Seems to be conflicting info on the net . Just case colored a receiver, have read I should temper at 400 F for 1 hour other sources don't mention tempering. Anyone have any experience? The receiver is a military RB in 12.7X44R.

Whats confusing me is since case hardening is surface hardening by adding carbon the the surface would the rest of the part not remain soft anyway and so not need tempering? Or am I misunderstanding something

 

[trevj]

What range you gonna test fire that at? Just curious.

Yer heat treating a rifle action, without having a clear knowledge of where you are going, and exactly how? I mean, low pressure rounds and all, but isn't this the sort of thing you should have a handle on before it goes into the fire?

Nice!

Cheers
Trev

 

[tiriaq]

Case hardening leaves a dead hard surface. IF the receiver was made of very low carbon steel, it will not have been affected by the quench. On the other hand, if the steel had enough carbon, it will have hardened.
Drawing at 400 wouldn't harm the case, wouldn't hurt very mild steel, would reduce core hardness a bit if it did harden. Would a 400 draw be adequate if the recever did through harden? I don't know.

 

[T M G Services]

Hi
The simple answer to you question is NO
Color Case Hardening and Hardening & tempering are different processes
In Hardening &Tempering the metal has a higher carbon content therfore you heat to the required temp & quench , The part can now be temperd if required by heating to the required temp [ IT VARIES DEPENDING ON USE ]

 

[juanvaldez]

Hi
The simple answer to you question is NO
Color Case Hardening and Hardening & tempering are different processes
In Hardening &Tempering the metal has a higher carbon content therfore you heat to the required temp & quench , The part can now be temperd if required by heating to the required temp [ IT VARIES DEPENDING ON USE ]

That was my understanding above but wanted to double check since I see some are mentioning tempering after the quench. (Marlin Website)

 

[juanvaldez]

What range you gonna test fire that at? Just curious.

Yer heat treating a rifle action, without having a clear knowledge of where you are going, and exactly how? I mean, low pressure rounds and all, but isn't this the sort of thing you should have a handle on before it goes into the fire?

Nice!

Cheers
Trev

trial by fire

 

[trevj]

trial by fire

Yer braver than me, then. Or something.

I'd want to have all my ducks in a row before I'd be doing anything with parts that could hurt me. Or someone else.
You planning on keeping this one forever? Selling it?

IIRC the guy on the marlin site was using the bake afterwards to ward off any potential over-hardening that he may have produced. Did you email him and ask?

Cheers
Trev

 

[T M G Services]

Hi
Just a comment on you pic Looks Good but its not gone through a color case hardening process ,Two much color [ Torch Maybe

 

[juanvaldez]

Hi
Just a comment on you pic Looks Good but its not gone through a color case hardening process ,Two much color [ Torch Maybe

??? Not sure what you mean? It spent 2.5 hours in a coal heated forge inside a piece of 4 inch pipe with a cap welded on one end and plate clamped to the other. Packed inside with it was charred bone meal, a leather glove, some hooves I bought at a pet store, 1 antler from a deer I shot a few years ago and some oak charcoal. I quenched in a bucket of distilled water with about 1/2 a cup of pottasium nitrate added. Aeration was with my compressor hooked into a length of garden hose with some holes punched in it.

Is that not case color hardening?

 

[BUSHMAN79]

R-b Action

Case hardening leaves a dead hard surface. IF the receiver was made of very low carbon steel, it will not have been affected by the quench. On the other hand, if the steel had enough carbon, it will have hardened.
Drawing at 400 wouldn't harm the case, wouldn't hurt very mild steel, would reduce core hardness a bit if it did harden. Would a 400 draw be adequate if the recever did through harden? I don't know.

The Swede Rolling Block would be maleable iron, not steel.

 

[T M G Services]

Your Method is good but temp to low need to be 1100 deg min with soak time of at least 3hr min to allow absorption of the carbon ,To do this in a Forge keeping control of temp is tough, In days gone by the Blacksmiths used ground up coal as the carbon source in there crucible & would heat for days this would then give the desired absorbtion. The quench would the give that desired mottled pattern, Sorry not trying to be critical

 

[juanvaldez]

Your Method is good but temp to low need to be 1100 deg min with soak time of at least 3hr min to allow absorption of the carbon ,To do this in a Forge keeping control of temp is tough, In days gone by the Blacksmiths used ground up coal as the carbon source in there crucible & would heat for days this would then give the desired absorbtion. The quench would the give that desired mottled pattern, Sorry not trying to be critical

TMG...thanks I just don't get what you mean by the torch?

Your right temp control was difficult especially since I was only going by the crucible color. I am quite certain I was over 1100 since I did have the entrie crucible at a dull to medium cherry. I used the speed control on my blower to try and control temp

 

[mooncoon]

Based on some of your comments, I think we need to go back to what tempering is; it is heating iron/steel red hot and quenching to make it brittle hard (assuming it has enough carbon to be heat treatable) and then reheating the metal to soften that brittleness to a working hardness. The amount that you heat it to depends on its intended use.
It would not hurt and might benefit your receiver to reheat it to 400 - 450F in case the receiver is high carbon in the middle and that temperature would leave the surface still quite hard and scratch resistant. The big risk in the original case hardening is of warping the frame during the quench. The risk of heating the receiver to high following the initial casing is that you will reoxidize the receiver and lose the case colours to all one colour depending on how high you reheat to.

cheers mooncoon

 

[juanvaldez]

Based on some of your comments, I think we need to go back to what tempering is; it is heating iron/steel red hot and quenching to make it brittle hard (assuming it has enough carbon to be heat treatable) and then reheating the metal to soften that brittleness to a working hardness. The amount that you heat it to depends on its intended use.
It would not hurt and might benefit your receiver to reheat it to 400 - 450F in case the receiver is high carbon in the middle and that temperature would leave the surface still quite hard and scratch resistant. The big risk in the original case hardening is of warping the frame during the quench. The risk of heating the receiver to high following the initial casing is that you will reoxidize the receiver and lose the case colours to all one colour depending on how high you reheat to.

cheers mooncoon

Thanks MC, I understand what tempering is and why you do it. But drawing of temper seems contradictory to one of the main reason of why you are case color hardening to begin with...low carbon steel.

 

[trevj]

TMG...thanks I just don't get what you mean by the torch?

Folks, some that had their shingle hung out as gunsmiths, would color metal up by playing a torch over the surface after it had been polished up. It looked somewhat like color case, to anyone that had no idea what they were looking at. Since it was neither durable, or hard...
Effectively just an oxide layer created by heat and oxygen. Same colors as used to judge temper when heat treating, blacksmith style.
That's what he was talking about,"torch" I think.

The colors turned out pretty decent for a low tech effort. I'd be some leery of having things come apart. Nothing wrong with flying by the seat of your arse when you are making parts that won't hurt someone if they fail.

Knowing the temperature, as well as the composition of the material you are case hardening, is fairly important, IMO. If you expect to get results you can rely upon, anyway.

Cheers
Trev

 

[mooncoon]

Thanks MC, I understand what tempering is and why you do it. But drawing of temper seems contradictory to one of the main reason of why you are case color hardening to begin with...low carbon steel.

If you knew for absolutely sure what the receiver was made of and knew that it was a low carbon iron, drawing the temper would serve no purpose. In this case you have no way of knowing for sure what the receiver is made of nor how deeply the original carborizing has penetrated and drawing the receiver to 400 -450 would make hard areas of the interior of the metal, less prone to breaking, maybe. Trouble is that if you really wanted to be absolutely sure, you would probably have to heat the receiver to just beyond dark blue (roughly 680 F inspite of what the blacksmithing books say) but that would defeat the hardening of the surface as well as destroy the case colours

cheers mooncoon

 

[juanvaldez]

Folks, some that had their shingle hung out as gunsmiths, would color metal up by playing a torch over the surface after it had been polished up. It looked somewhat like color case, to anyone that had no idea what they were looking at. Since it was neither durable, or hard...
Effectively just an oxide layer created by heat and oxygen. Same colors as used to judge temper when heat treating, blacksmith style.
That's what he was talking about,"torch" I think.

The colors turned out pretty decent for a low tech effort. I'd be some leery of having things come apart. Nothing wrong with flying by the seat of your arse when you are making parts that won't hurt someone if they fail.

Knowing the temperature, as well as the composition of the material you are case hardening, is fairly important, IMO. If you expect to get results you can rely upon, anyway.

Cheers
Trev

Well as far as composition goes I've heard everything from low to no carbon steel. AFAIK The original finish was CCH and I have seen several reworked with a CCH finish so have some confidence that it will not fly appart. Everything I've read seems to indicate that since the steel is low carbon the hardening is limited to the outer few thous that will absorb carbon from the pack and therefore the quench will not turn the rest of the receiver brittle. You are right though caution is still the best course and I will strap her to a tire for proof testing. The load for this gun is very low pressure if the felt recoil is any indication. Shooting a lee 400 grain cast bullet over 28 grains of 4198. Recoil is substantially less then a full case of 2f

 

[juanvaldez]

Folks, some that had their shingle hung out as gunsmiths, would color metal up by playing a torch over the surface after it had been polished up. It looked somewhat like color case, to anyone that had no idea what they were looking at. Since it was neither durable, or hard...
Effectively just an oxide layer created by heat and oxygen. Same colors as used to judge temper when heat treating, blacksmith style.
That's what he was talking about,"torch" I think.

The colors turned out pretty decent for a low tech effort. I'd be some leery of having things come apart. Nothing wrong with flying by the seat of your arse when you are making parts that won't hurt someone if they fail.

Knowing the temperature, as well as the composition of the material you are case hardening, is fairly important, IMO. If you expect to get results you can rely upon, anyway.

Cheers
Trev

Well as far as composition goes I've heard everything from low to no carbon steel. AFAIK The original finish was CCH and I have seen several reworked with a CCH finish so have some confidence that it will not fly appart. Everything I've read seems to indicate that since the steel is low carbon the hardening is limited to the outer few thous that will absorb carbon from the pack and therefore the quench will not turn the rest of the receiver brittle. You are right though caution is still the best course and I will strap her to a tire for proof testing. The load for this gun is very low pressure if the felt recoil is any indication. Shooting a lee 400 grain cast bullet over 28 grains of 4198. Recoil is substantially less then a full case of 2f