pipe for HT

jdm61

jdm61

itinerant metal pounder
Joined
Aug 12, 2005
Messages
47,357
I have heard a number of folks say that they use a length of capped steel pipe in their forge for heat treating so that the flame does not directly contact the blade. How do you do such a setup? I have tried making a little shelter out of high temp ceramic tile, but the tile soaks up a lot of heat and it is a PITA get big blades in. I have an 11 1/2 x 2 inch bowie blade on the bench that MUST be perfect so I would think that I would need 3 inch pipe.
 
When you place a piece of pipe (tube) through a gas forge, or a capped piece of pipe in a coal forge, it is called a muffle.You are creating what is basically a gas HT oven.If you place a thermocouple probe in the tube, and have the controller hooked to a gas solenoid valve, you can regulate the temperature in the pipe to a very close tolerance. It keeps the flame away from the blade and allows a much more even heating of the entire blade. An 18" section of schedule 80 stainless steel or Black Iron pipe (NOT galvanized) will do the trick. Place the pipe in/through the forge (use some firebricks to hold it in the center if needed) and bring it up to heat.When heated,place the blade in the muffle and allow it to come up to the desired temperature. Soak for the required time and quench as normal. No more overheated edges and tips ! It greatly reduces scale,too. Some people put a few wood chips in the muffle to consume the excess oxygen.
Stacy
 
Stacy speaks the truth! I have a small piece of firebrick inside of mine with a slot to hold blades edge up, and I toss some wood in with it. The scale is negligable. The only thing is that in MY forge the rear is a little more hot than the front so I still have to be careful of overheating the tips.

-d
 
Thanks for the head ups on not using galvanized, Stacy. Do you NOT want to use a capped muffle in a gas forge?
 
bladsmth said:
When you place a piece of pipe (tube) through a gas forge, or a capped piece of pipe in a coal forge, it is called a muffle.You are creating what is basically a gas HT oven.If you place a thermocouple probe in the tube, and have the controller hooked to a gas solenoid valve, you can regulate the temperature in the pipe to a very close tolerance. It keeps the flame away from the blade and allows a much more even heating of the entire blade. An 18" section of schedule 80 stainless steel or Black Iron pipe (NOT galvanized) will do the trick. Place the pipe in/through the forge (use some firebricks to hold it in the center if needed) and bring it up to heat.When heated,place the blade in the muffle and allow it to come up to the desired temperature. Soak for the required time and quench as normal. No more overheated edges and tips ! It greatly reduces scale,too. Some people put a few wood chips in the muffle to consume the excess oxygen.
Stacy
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Stacy,
Can you suggest a source for the thermocouple and the gas solenoid valve please? I would really like to get this part of my process under as much control as possible, without going to the expense of a heat treat oven for the time being.
 
i got a 3" x 20" or so piece of black iron pipe. I won't be needing fire bricks to hold it in place. I had to "shave" it a bit on one side with the KMG to get it to go throught the opening on the forge. I put two pieces of heat resistant tile in it as a shelf and will try it out this weekend.:thumbup:
 
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