Help with Steel

[Stephen Downie]

Ray,

Thanks again for answering all these rookie questions. I'm at the phase where a little bit of knowledge is a dangerous thing. I'm hoping to be over the worst of it soon! Maybe I'll chop the pipe down a bit for a smaller forge and put in a smaller back door. Just a thought though, how would one quench a sword a bit at a time and not mess up the temper when you heated the next portion of the blade up?

Back to Pyrometers for a moment, how would you position one to get an accurate read of the forge, or would you suggest a portable version for checking different areas in the forge.

[Ray Rogers]

You wouldn't quench the blade a section at a time - that would be a disaster. You can raise the whole blade to temp in a short forge by simply running it in and out through the forge until the whole thing is hot enough. This is how most guys would heat a sword for quenching. For forging, you generally just heat the part you're working on because the blade will cool too much before you can hammer all of it anyway and it's not goot to heat the steel any more times than necessary.

A thermocouple will only measure the temperature in the immediate area of where it is placed and you'll find that your forge has some areas that are hotter than others. In my forge, for instance, I can measure a variance of 300 to 400 F between the front half and the back half of the forge during most of the first 45 minutes the forge is running. My burners are at the rear of the forge so this is to be expected. After full heat is achieved the difference drops to about 100 F or less.

So, what all that means is, where will you put your blade - that's the area you want to measure. BTW, make sure your burners do not spray directly onto your blade or you won't have a blade for very long. The burners heat the forge, the hot forge heats the steel. If you follow that rule then you can measure the temp in any area that is expected to have the same temp as the place your blade is sitting. That's important because you can't actually stick your thermocouple through the front door to reach an interior area - a) because you'll probably get a reading that's not accurate and b) because it won't be long before you melt your thermocouple or its sheathing.

To solve these problems, I installed a couple of thermocouple wells in my forge, one at the rear and one in the middle where my steel sits most of the time. A thermocouple well is simply a tube that runs from the outside of the forge, through the wall and insulation, and slightly into the hot area inside. I made mine from 1/2" stainless rod, drilled a hole in the center, and used refractory glue to hold them in place (because they will burn out eventually and need replacement). Just run the thermocouple through the hole take the reading and pull it out. Some guys leave them in all the time, that doesn't work for me but maybe it will for you. Anyway, it doesn't seem necessary. After you get familiar with your forge you will probably stop taking readings because you won't need them most of the time. The only time I worry about being that precise is when I'm working a steel like 52100 that only has a 100 F window in which in can be forged or welded....

[pipecrafter]

Originally Posted by Ray Rogers

A castable forge takes much longer to build and the expense is considerable by comparison to wool. They will take much longer to reach welding temperature, often 30 minutes to one hour depending on the mass of castable involved. The good news is, once they get to temp they hold it very well so gas pressure can then be reduced thus saving fuel. These forges work better for long forging sessions, say a minimum of half a day. They are also useful for annealing steel as they cool down very slowly.

Awesome info, Ray. Thank you. I think I'm going in the right direction now.