Jump to content
Sign in to follow this  
Gerhard

HT chamber in gas forge?

Recommended Posts

Howdy

I made a chamber from rectangle tube to use in my gas forge for heat treat, same as I do in the coal forge.

I can't get welding heat in my gas forge but it's hunky-dory for just forging,  but I couldn't get the chamber, nevermind the blades, nearly hot enough.

My suspicion is the roof gets all the heat, so the floor of the forge and the chamber  never gets hot enough.

Has anybody tried this? Will more heat work?

How much performance do you loose due to lost carbon going straight in the forge? Measurable?  

Share this post


Link to post
Share on other sites

I used to do this to limit scale during heat treating, but found it wasn't much of an advantage in my particular forge.  (With my particular setup it is just easier to use anti-scale compound)

I never had any trouble getting the tube hot though.  How much room do you have between the top of the tube and the roof of the forge?  I had a lot of room over the tube for combustion.

  • Thanks 1

Share this post


Link to post
Share on other sites

Small tube but also a small forge.....takes up more than 2/3 so that's probably the problem.

Share this post


Link to post
Share on other sites

My tube was kind of small.  I think it was about 25mmx75mm

That gave me a lot of air space for combustion over the tube, but didn't give me much room inside to manipulate the blade.  Even with the tube, I found the blade didn't heat evenly, so I was always trying to move it around in that cramped space.  In the end I just stopped using it :)

 

Share this post


Link to post
Share on other sites

I've tried the tube as well and had a similar experience to Brian.  It didn't seem to help with how evenly the blade heated, and I still couldn't see re/decalescense while the blade was in the forge.  Now I will typically run my flame a bit rich and just move the blade across the mouth of the forge in the dragons breath with the shop lights turned off.  It took some practice, but now I get a much more even heat this way and it's a lot easier to see the phase change.

Share this post


Link to post
Share on other sites

The tube does work best in a solid fuel forge, but it can work fine in a gas IF the forge is big enough.  You need a lot of space around the tube to get the even heat effect.  The smaller volume forges we typically use don't have enough free air space.  

It is also imperative that one end of the tube be sealed.  But you knew that. 

Share this post


Link to post
Share on other sites
On ‎9‎/‎13‎/‎2018 at 12:32 AM, Gerhard said:

How much performance do you loose due to lost carbon going straight in the forge? Measurable?  

It depends on how much grinding you have left to do and what sort of flame you have (oxidizing or reducing). The carbon loss going straight into the forge with no baffle tube will generally be limited to the outer surface and not go too deep. When I did my HT this way, I ground to about 120-150 grit and went for quench. The subsequent 120- 400 grit grinding/sanding was more than adequate to get into the "good" steel. Bladesmiths used to say "the best steel is below the surface". Use a reducing flame and the loss will be minimal anyway.

You also do not want the blade in direct line with the flames coming off the burner. Try to keep the blade off to the side of the forge where it gets heated by ambience, not by direct flame contact.

On ‎9‎/‎13‎/‎2018 at 1:04 PM, Alan Longmire said:

It is also imperative that one end of the tube be sealed.  But you knew that. 

Nope. I did not know that. The baffle tube I use has both ends open, but the back end is inside the forge where the front end sticks out the door. My venturi forge also has a back door that remains closed in this operation, so that probably works the same as sealing one tube end.

Edited by Joshua States

Share this post


Link to post
Share on other sites

Last time I had the forge lit I struggled a bit, does it make sense that the steel will get hotter quicker if the forge is running oxidizing?

 

All the tubes I've used were sealed at one end, and I chuck in a few bits of charcoal.

I'm busy with 3 smaller knives so a smaller diameter pipe could've and might work, will give it a try.

3 hours ago, Joshua States said:

It depends on how much grinding you have left to do and what sort of flame you have (oxidizing or reducing). The carbon loss going straight into the forge with no baffle tube will generally be limited to the outer surface and not go too deep. When I did my HT this way, I ground to about 120-150 grit and went for quench. The subsequent 120- 400 grit grinding/sanding was more than adequate to get into the "good" steel. Bladesmiths used to say "the best steel is below the surface". Use a reducing flame and the loss will be minimal anyway.

I don't worry about 5160 since it's deep hardening, my personal experience taught me the better steel comes out after a few sharpenings.

Problem is these last blades were all old files......I've turned into a bit of a hamon-whore :P .......not sure how deep 1095 hardens.....?

Share this post


Link to post
Share on other sites

1095 fully hardens about 0.7 - 1 mm deep.  Coming from both sides of a blade, you get full through-hardness anywhere the blade is about 1.4 - 2 mm thick or less. 

  • Thanks 1

Share this post


Link to post
Share on other sites

Another thing to keep in mind is that grain size effects hardenability.  The smaller the grain the less deeply the steel like 1095 will harden.  This is something to keep in mind if you run into a situation where you just can't seem to get that hamon to show up.  You might have overheated the steel and grown the grain large enough that the blade will harden all the way through.

Doug

  • Thanks 1

Share this post


Link to post
Share on other sites

Thanks guys, I should be fine then on these little blades.

I'm getting a bit smarter, remembered to do the final grind followed by etch before soldering on the brass bolsters.

I've got a hamon on all three, one very nice and two just there, but it seems I got the heat treat good....

Did some inadvertent testing, don't know what was going on but all three blades got caught by the polisher and flung tip first into the cement floor.... 

Share this post


Link to post
Share on other sites
9 minutes ago, Gerhard said:

Thanks guys, I should be fine then on these little blades.

I'm getting a bit smarter, remembered to do the final grind followed by etch before soldering on the brass bolsters.

I've got a hamon on all three, one very nice and two just there, but it seems I got the heat treat good....

Did some inadvertent testing, don't know what was going on but all three blades got caught by the polisher and flung tip first into the cement floor.... 

watch out that tip first into cement floor doesnt become tip first into thigh or chest. can happen so quick

Share this post


Link to post
Share on other sites

Ja.......and I was wearing my garage Crocs......

It's happened once or twice, aware of the danger and hate the damage to a blade at that stage......3 in a row almost feels like the universe sending a message :-P

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×