Correct forging temps for 5160???

[Rick Baum]

I am in the process of forging my first blade. It has been an incredible amount of work so far and I think that I just found out why. For some reason I thought that all of the forging work was supposed to be at a temperature below critical (non-magnetic). So I have been working the steel for a total of almost 4 hours at below critical temps. Anyone have a new arm for me??? So, after last nights attempt to draw out the tang (unsuccessfully) I decided to pull out some reading material to double check heat colors and recommended temps for normalizing and anealing. Low and behold... Wayne Goddard says that for 5160, he likes to forge between 1600 to 2200 degrees and that the steel becomes non-magnetic for normalizing and anealing at around 1525 degrees. I thought that temps above critical causes grain growth and is supposed to be avoided at all costs Can you guys please straighten me out? Have I ruined the steel working at too low of temps?

Rick

 

[Ed Fowler]

When I forge 5160 I use the same rules I apply to 52100. 1625 f is the top temp. You can go as high as 1725 but at that temp you are very close to growing grain and losing all you gain by low temp forging. 1625 is above critical but there is very little grain grain growth if any. You can tell when you are at 1625 by watching the size of the scale that forms. You are above magnetic, but not much, the sacle will come off in small flakes, like medium to small sized snow flakes. Continue to work the steel until it quits moving and starts to bounce and ring, then re-heat.

It is a matter of balancing your forge temp to moving steel. Low temp takes a lot of elbow grease, but the result is worth it. Ultra low temp (like you were doing) produces some extremely interesting grain patterns, as seen by the etch, but it is very slow going. The increase in performance is not a great deal over the 1625 forging temp produced blades. The low temp requires a lot of thermal cycles, but there will be no measurable carbon loss.

You have not hurt the blade unless you have caused some cracks in the steel.

Don't be bashful about heating the blade to above critical and quenching to a black heat during the forging cycles, this will improve performance.

It does not hurt and improves the steel to throw in a couple of complete normalizing cycles, (above critical to room temp) along with forging the blade.

High temp forging is more economical both time and labor wise, but expensive in performance cost.

The most significant rule --- enjoy what you are doing. If performance is your goal, low temp is fun, if production (a lot of knives) is your goal, high temp is mandatory.

 

[Rick Baum]

Thanks Ed! I really appreciate the advice and encouragement. I'm sure that I'm speaking for a lot of people here on this forum when I say that I appreciate your willingness and generosity for passing on your knowledge that you have worked many years to gain.

I have been normalizing at the end of each of my forging sessions. I think that I will do a quench tonight, it will probably tell me if I have developed any cracks from forging at too low of a temp. Better now than when I'm done forging and potentially waisted more time, not to mention the performance gains. A couple of questions about the quench during the forging process...

Do you do an edge quench or a full quench? Do you aneal or normalize after the forging quench, or just reheat and start pounding?

In regards to watching the scale... At the heats that I have been forging at prior to tonight, I have been getting very fine scale, about the size of a pin head or smaller. Will the scale you are talking about be larger? Is there a way to tell if my forge is setup properly by the size of the scale that I'm getting?

Thanks,
Rick

 

[Rick Baum]

I'm down to forging the tang now so I upped the temp to make things easier. Worked out great!

I was having trouble trying to draw out the tang on the horn of my small anvil. My problem was really two fold. The first problem was too low of a forging temp. The second was my cruddy little anvil. I found a 1 foot section of railroad track, cleaned it up a bit with some files and voila. I now have a tang. Now I just need to fine tune the blade a little and it's time to normalize, aneal and profile.

Ed, You were absolutely right about the production forging temp vs. quality forging temp. I used a slightly higher than critical temp to forge the tang. Compared to the work that I have put in on the blade portion, it was a breeze (partly because of the anvil change I'm sure). I am going to finish the blade portion at the same (ultra low)temp that I have used so far. I don't want to change anything now for the sake of future comparison. I also did a quench on the blade per your recommendation and Bill's. I'm hoping that if the blade was going to crack due to the ultra low forging temp that it would have done it tonight. So far so good, no cracks. I also see what you mean by the scale size and the ringing and rebound of the steel.. Thanks!

Thanks for everyones help!

Rick

 

[Ed Fowler]

Rick: While forging I quench the front 2/3ds of the blade, just because the blade is still attached to the billet and more won't go in the oil. I believe the front 2/3ds of the blade is plenty enough to quench as this catches all of the cutting edge and a lot of the spine. the part left out is only needed to be tough and strong. When forging the tang, the front is repeatedly quenched to keep it cool. Again this doesn'thurt a thing. The whole goal in forging is to enhance the potential of the blade while doing nothing to hurt performance. It takes a while to learn what does what, but when it all comes together you can smile a lot.

I learned a lot about gas forges watching a lady blow glass. They are the king of the hill at setting a gas forge. Wayne Goddard mentioned this to me and next time I could I watched very closely. After the forge is hot, I turn down the gas and then watch the flame coming out of the hole in the front of the forge and set it so the majority of the yellow tail is gone. If the forge cools down too much, I re-adjust. The forge and you can communicate, you just have to learn its language.

I believe that the tone of the anvil also contributes to the nature of the blade. This is a very fine point and not an event that Rex feels could be scientifically evaluated. It is just a feeling I have and may someday attempt to explore.
It may be that a dead anvil could be better than a live one, just something to keep in mind and wonder about. Maybe when you are my age the science will have become available to define more variables. In the mean time we have a lot to have fun with.