The thread about "How hot it too hot?" is a good one. I thought this related but different aspect could use it's own thread.
Just this week I have spent a lot of time in the blacksmith forge and discussing working temperature at length as it applies to high carbon steel. I agree with Kevin's assessment of the damage that is done at the extreme end of a steel's tolerance for heat. When it gets into the white range, it is about to start being damaged beyond repair. So, yellow or bright yellow is about as hot as I use as the high end of the heat range. If the steel could not tolerate that, then a lot of Damascus blades would have to be considered "burned up" since a lot of makers heat to well over 2000 degrees F when welding.
Heat is a tool the same as a hammer or a pair of tongs is a tool. You should use the appropriate heat for a given task the same a using an appropriate tool. For instance, when a bar of steel is first placed into the forge, it has the most mass and therefore would require an appropriate high heat for good steel movement. This heat would be below the danger of burning point but high in the steel's range of tolerance.
When you think about it, the change from a rectangular bar into a blade shape is not very extreme in the way of metal movement when compared to most BLACKsmith projects. So, in my opinion, The heat also should remain out of the extreme range. The highest heat used in the whole process would logically be used when forging a square point into a tip and generally lessening the heat as the blade gets nearer to final shape. Heats such as these are within the high carbon steel's tolerance AND allow the needed manipulation from rectangular bar stock to blade.
When EXTREME manipulation by forging is done to carbon steel, it is especially essential that the appropriate heat is used. For instance, if you were to have a 2 inch cube of HC or even a large ball bearing and want to forge a blade, you would be dramatically changing the cross section and length of the material, so you would NEED to heat it to right at welding heat to move it efficiently so as to get closer to something manageable in as few high heats as possible. Then the heats can also be lowered accordingly.
Control of the heat whether in a gas forge or coal is a mark of a good bladesmith.
Morning Lin,
This absolutely was the case for me, i was forging down some 1.75 inch round 52100, it's pretty stiff stuff and it hardly felt like my 50lb little giant was even touching it at first despite working it at yellow heat. Now my little blade forging forge doesn't get hot enough fast enough to move that kind of material so i used my welding forge(propane) and once i got a manageable size billet to start my knife proportioning i just figured id keep on with the hot forge instead of switching over.
Once this forge is up to temp, it is very difficult to get it to stay running at anything less than 2300 without it sputtering so i just tried to use shorter soaks as i progressed to finish dimension. I like to forge as close as i can to test myself i guess and progress in this art, but i wonder if i should leave the tips a little heavier? Is that common practice? Then just leave distal taper to the grinder? Well that's my morning thought anyway. Thanks for listening.
Jesse,
I heard Bob Kramer MS say that there are Three T's: Time, Temperature, and Technique. While this is understood and taught in bladesmithing, I would point out that there is an interplay of those three things, each of which we should strive to gain control of. Primarily I would address the first two, time and temperature.
First of all, We have to have as much control over our heat source as possible whether it be a propane forge or coal forge or any other source of heat. The more control we have of the heat, the less we have to worry with technique and timing ( in and out of the forge ). Where one of the three T's are less in control, the other two have to step up and be very much in control. The farther out of balance these get, the more likely things will go wrong and that translates into a lower standard of consistency.
I often use a coal fire to forge by. But, I am used to it and know how to use it thus I consider my control over my heat to be good, but my sense of timing has to be good as well because of the nature of a bellows operated coke fire. Another smith might need a propane or induction forge to have the control needed. Some actually regulate their forge burner to maintain a set temperature so as to never get above their chosen forging temperatures. In such cases, timing becomes less an issue.
In about every case where we are having issues, one or more of the three things mentioned are lacking in control.
To answer your question, it is common for the tip to be left thick till near the end of the forging process so it's mass can tend to withstand the heat better, then refine it at a lower temperature. You mentioned you have a small forge as well as a big one. I do as well. I use the big forge for heavy reduction and switch to the small one as I need to in order to keep control of my heat. Everyone's shop is set up slightly different but the principles are the same.
Thank you men, as always I learn something every time I log in.
