Bob Dunlap--Metalurgy for Gunsmiths - Page 2

BobCat45 · June 1, 2015, 02:19 PM

You can quench 4140 in water but it will probably quench crack, you are much better off quenching in oil.

But if you do water quench and it does not crack, temper it immediately - or it likely will crack, just sitting around.

Gunplummer · June 1, 2015, 02:30 PM

OK, so just how do you do that when color case hardening? As I said before, I never found any reference to water quenching 4140. It is too uncontrollable. I have seen photos of '99 Savages that are color cased. It is called color case hardening, not color all the way through hardening. Are we back to cyanide again?

Jim Watson · June 1, 2015, 02:39 PM

Mr Turnbull says he can case harden 4140 at a temperature just below its effective heat treatment temperature.

BobCat45 · June 1, 2015, 02:43 PM

I don't know - never done color case hardening.

Pack carburizing I've done, and it entails long time heating in high-carbon material http://www.rosemill.com/category_s/48.htm cooling, then quench and temper - you may get colors but it is not specifically a color case hardening process.

If the 4140 part has few sharp corners (stress raisers) it might water quench without cracking but it is real chancy.

Do you need to water quench (as opposed to oil quench) when color case hardening? And - 4140 can develop real good strength on it's own, I can see wanting to case harden for wear resistance or appearance, but is the process commonly applied to 4140?

Gunplummer · June 1, 2015, 02:49 PM

I am assuming we are talking below 1550 degrees. What are his thoughts about what '99 Savage receiver material is? That is what we are trying to find out here.

Dixie Gunsmithing · June 1, 2015, 02:57 PM

My suggestion, would be to e-mail or call someone who is very knowledgeable in case hardening. Jim mentions that Turnbull says he can do it, but what is his complete process? That's why I mentioned experimenting with scrap, to see what can be done.

I always sent frames off, that needed it done, so I couldn't say, and none were 4140. I understand the process, on regular low carbon steel, but 4140 is a different beast.

Gunplummer · June 1, 2015, 02:59 PM

Pack carborizing is pretty much like color caseing. I never used charcoal, just ash from all kinds of stuff I burned up. That is where the carbon comes from. I then threw it in water (Pack material with it) with an 02 source (Air hose) bubbling the water. Never drew it back, I figured it would wreck the color, but I don't know about that.

BobCat45 · June 1, 2015, 03:16 PM

Gunplummer, I read (but do not "know") that one of the things besides carbon / charcoal in the pack carburizing stuff is barium carbonate, which comes from bone ash, and promotes formation of CO versus CO2. Raises carbon potential, making more carbon diffuse into the steel and less get lost as CO2.

I've also read that the air bubbling in the water quench is to promote temper colors - the actual color in the color case - by varying the oxide thickness that forms over the carburized case.

And - the guy who wrote that did not mention subsequent tempering / drawing, and implied that since the underlying steel was low carbon, they just quenched and left it at that - case was hard, core soft, no need to temper. But you would not do that to 4140, it would be hard and brittle all the way through (or very deep anyway).

Gunplummer · June 1, 2015, 03:16 PM

Who in the world is knowledgeable about color case hardening 4140? This '99 Savage thing has been bugging me for years. Even if it is not 4140, it has a high carbon content. Charts and grafs are all well and good, if you know what you are dealing with.

Yeah Bobcat, now you see where I am coming from! You burn all kinds of stuff up and crush it down. Chicken bones, scrap leather, nuts, leaves, I even tried using peach stones and apricot pits because I heard there was cyanide in them. It takes forever to round up enough stuff for a good batch. I never could get the bright yellow and golds that I saw on guns that were cyanide cased. If you look at the newer charcoal done guns, there is not much yellow on them either.

June 1, 2015, 02:30 PM	#27
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	OK, so just how do you do that when color case hardening? As I said before, I never found any reference to water quenching 4140. It is too uncontrollable. I have seen photos of '99 Savages that are color cased. It is called color case hardening, not color all the way through hardening. Are we back to cyanide again? Last edited by Gunplummer; June 1, 2015 at 02:40 PM.

June 1, 2015, 03:16 PM	#34
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	Who in the world is knowledgeable about color case hardening 4140? This '99 Savage thing has been bugging me for years. Even if it is not 4140, it has a high carbon content. Charts and grafs are all well and good, if you know what you are dealing with. Yeah Bobcat, now you see where I am coming from! You burn all kinds of stuff up and crush it down. Chicken bones, scrap leather, nuts, leaves, I even tried using peach stones and apricot pits because I heard there was cyanide in them. It takes forever to round up enough stuff for a good batch. I never could get the bright yellow and golds that I saw on guns that were cyanide cased. If you look at the newer charcoal done guns, there is not much yellow on them either. Last edited by Gunplummer; June 1, 2015 at 03:26 PM.

June 1, 2015, 02:19 PM	#26
BobCat45 Senior Member Join Date: May 18, 2004 Location: East Bernard, TX Posts: 523	You can quench 4140 in water but it will probably quench crack, you are much better off quenching in oil. But if you do water quench and it does not crack, temper it immediately - or it likely will crack, just sitting around.

June 1, 2015, 02:39 PM	#28
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	Mr Turnbull says he can case harden 4140 at a temperature just below its effective heat treatment temperature.

June 1, 2015, 02:43 PM	#29
BobCat45 Senior Member Join Date: May 18, 2004 Location: East Bernard, TX Posts: 523	I don't know - never done color case hardening. Pack carburizing I've done, and it entails long time heating in high-carbon material http://www.rosemill.com/category_s/48.htm cooling, then quench and temper - you may get colors but it is not specifically a color case hardening process. If the 4140 part has few sharp corners (stress raisers) it might water quench without cracking but it is real chancy. Do you need to water quench (as opposed to oil quench) when color case hardening? And - 4140 can develop real good strength on it's own, I can see wanting to case harden for wear resistance or appearance, but is the process commonly applied to 4140?

June 1, 2015, 02:49 PM	#30
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	I am assuming we are talking below 1550 degrees. What are his thoughts about what '99 Savage receiver material is? That is what we are trying to find out here.

June 1, 2015, 02:57 PM	#31
Dixie Gunsmithing Moderator Emeritus Join Date: April 27, 2013 Location: Ohio Posts: 1,923	My suggestion, would be to e-mail or call someone who is very knowledgeable in case hardening. Jim mentions that Turnbull says he can do it, but what is his complete process? That's why I mentioned experimenting with scrap, to see what can be done. I always sent frames off, that needed it done, so I couldn't say, and none were 4140. I understand the process, on regular low carbon steel, but 4140 is a different beast.

June 1, 2015, 02:59 PM	#32
Gunplummer Senior Member Join Date: March 11, 2010 Location: South East Pa. Posts: 3,364	Pack carborizing is pretty much like color caseing. I never used charcoal, just ash from all kinds of stuff I burned up. That is where the carbon comes from. I then threw it in water (Pack material with it) with an 02 source (Air hose) bubbling the water. Never drew it back, I figured it would wreck the color, but I don't know about that.