Heat Treating Help

[ALW]

I'm a novice at knife making so I hope any advice I get here can help out someone like myself.  I just heat treated a couple of blades over the weekend.  They are made from 1/8-inch O1 steel.  

    I have pretty simple setup.  A small washtub forge with a hair dryer for an air source.  I used vegetable oil heated to 130 degrees for the quenchant.  I have no way of measuring the temperature accurately so I'm just using a magnet to find when it demagnetizes and to some degree the color of the steel.  I heated the blades until they were non-magnetic then let them cool back down to try and normalize the steel.  I reheated the blades to non-magnetic again then let them soak for another 5 minutes.  Then straight to the quench tank until they no longer were bubbling.  I checked them with a file and it skated across.  I then tempered them in the oven for two, two hour cycles at 400 degrees letting them cool to room temperature between.  Now, here's my question.  After I quenched them parts of the blade had small "blisters" on it.  Mainly on the blade area where the bevel is, but also on parts of the tang.  What causes this?  Here's a picture (I hope) of what it looks like.
 

    I'm sure my heating/quenching process is not exact.  But how can someone with a really basic setup like mine get a better quality from their quench?  Is what I'm getting normal or is this being caused by my total inexperience?

    I've read a ton of posts here on heat treating and have tried to absorb all the good information.  And I have read from some that O1 steel is hard to get right without really good temp. control, while others seem to do really good with basic setups like mine.  I respect and admire the professionals here that make fantastic works of art and have put years in to learn the art so please don't take what I'm asking the wrong way.  But I don't have the means to get a really good setup to be able to control my temperatures or get the proper quenchant nor do I have the spare time to make hundreds of knives to test and fine tune my abilities, so are there some tips for a "shadetree" knife maker that can help me make a better blade?

    Sorry to be so windy but myself and a few friends have gotten the bug to make some knives and we are looking for all the help we can get with our limited time, money, and skill.  Thanks for any help.

Aaron

[DANA HOLMAN]

Aron
I'm new at this as well, I have a simple setup, one brick forge and veg oil, i used to do my knives, for one hr. but have switched to 2-2hr. cycles, as far as the blisters on the blade i've had the same problem you just haft to grind them off. that's why you leave plenty of steel before you heat treat.
i can't afford a klin right now either.
one day you should do a test knife to see what you steel is doing, i'm sure the other guys will chime in and help you
p.s. i did a rockwell test on a peice of 01 steel, heated treated, tempered 1 hour @ 400 degrees and came out with a test of 60.5 and 61 very hard for a knife, that's why i went to 2 -2hr cycles
good luck
dana

[Lin Rhea]

Aaron, I think it's just oxidation from having a very open atmosphere. Beiing in easy contact with lots of oxygen. It just surface pitting and can be sanded off. Just dont get it hot now. No hotter than your draw back temp, which was 400 degrees. This not unusual.

    You are much better learning the "shade tree" method and get it right than to have all of the technical jargon down and not understand it. One thing, If you are using a magnet, that's good, but I recommend doing all of this in a low light condition. A shed or something. When your magnet tells you it's ready, take a mental note of the color of the steel. Get to where you can recognize it, say if you dont have a magnet.
                             Lin

[Lin Rhea]

Dana,
     Did you check the Rockwell on your blade after the two hour draw?

    I cant help thinking that the Rockwell wont change much, if at all. In my opinion, the surface of the blade will have been drawn to it's rockwell in the one hour session. The additional hour insures that the whole blade, even the thickest parts, are drawn back.

  Generally speaking, you have to raise the draw temps, say to 410 or 420 to soften it a little more and get the Rockwell to read lower. Lin

[ALW]

Dana, I read your post about the hardness test you had done.  You are the one that I mentioned having good success with the O1 but I'm sure your setup is a lot better than mine.  I guess I was expecting the blade to come out nice and smooth with just some scale on it!  I'm actually going to get it tested tomorrow at work.  I'm friends with the guy that's the head of the steel lab!  LOL....  I'll post the results and see how well I did.

Lin, thanks for the advice.  Unfortunately the only place I can set my forge up is in the back yard.  I guess I can try it the next time late in the evening.  As far as the color goes, with it buried in the coals it's kind of hard to watch the color change.  I was afraid that pulling it out of the coals to look at it, the color might change too quickly in the air to get a good read.  Plus with this thin steel it seems that the steel gets "up to heat" extremely quickly.  It goes non-magnetic really fast.  Should I get a good fire going with the blower then turn the air off and put the blade in to let it start heating at a slower rate?  Then put the air flow back to it.  Does this do any good?  Also how do I control the environment (oxidation) in an open forge like this?  Is it all a matter of the air flow I have?  And how can I tell when I have it right?  Sorry for all the questions but I just want to produce a quality blade that I can use, give away, or put in the swap here.  I still have a long way to go.

By the way, I used the advice of, I believe it was KBA on here, about the two tempering cycles.  He posted some time back on another thread about the multiple tempering cycles to fully transform the steel structure (austenite) in case it wasn't completely transformed during the quench.  I think I'm stating what he posted correctly, in laymans terms.  He was much more detailed in the thread that I read though.

Thanks for the advice.  And any other advice is welcomed.  I'm just starting at this so I can use all the help I can get.

Aaron

[Lin Rhea]

Aaron, Yes, by all means, you can turn the air down or off after you get the fuel hot and let the blade absorb the heat at a slower rate. I imagine it will cut down on the orange peel effect too, since you have stopped the oxygen flow.

 I always come up to critical at a slower rate by turning the forge down. Here is another thing you can do. Place a 2 1/2-3 inch section of pipe directly in or on the fire, with the end open toward you and put the blade inside the pipe while heating. This creates a buffer between the super heated fuel and your blade, so it can come up to temp and have a little more time to soak and is less likely to burn the thiner areas of the blade. Lin

[ALW]

Thanks guys.  Well I got the blades tested for hardness today.  And I think I have a ways to go to get this right.  The blade I showed above tested at just over 58 Rockwell and the smaller blade I did tested at 59.5.  I don't think I got them hard enough at the quench.

I'm thinking now that I didn't get them hot enough even though I was worried I had overheated them.  The blade that came out at 59.5 was heated with coal.  The blade above was heated using hardwood chuncks for fuel.  I wonder if the coal fire got the smaller blade up closer to where it needed to be?  Or maybe I actually overheated them.  Who knows.  I guess I'll just have to make a few more from the O1 I have left and try heating it a little longer and see if that helps.

Anyway, thanks for the advice.  Lin I'll try the pipe trick next time and see how that works.  I guess the more knives you make the better you can refine the process.

Aaron

[kbaknife]

This statement sort of concerns me a little.


 

Originally posted by ALW:

  I reheated the blades to non-magnetic again then let them soak for another 5 minutes.    
     

How, exactly, did you control your temperature for this five minutes?
It would be extremely difficult, even for an experienced blacksmith, to maintain a constant temperature for any length of time in a forced air fire pot of coal or charcoal.
I wasn't there, so I TRULY have no idea what happened, but five minutes "soaking" in a coal forge COULD turn a piece of steel into a cinder.
And like Lin said, even if it wasn't up to austentizing temp, that period of time in a very highly oxodizing/de-carburizing atmosphere can wreak havoc with the steel surface.
Always a bunch of factors - isn't there?

[DANA HOLMAN]

sorry guys someone ran over the telphone box at work and my e-mail is out.
aaron you should take the advise from these two guys (lin and karl) they have tought my so much and they know what they are doing
lin to ansure your question when i did my test i had tempered it for 1 hr.
this is what i had heard, so the 20 knives that i've built have been tempered 1 hr. @ 400 degress.
now after i've talked to you guysand others' i use the 2 hr. tempering, but have not tested it yet.
thanks
dana

[ALW]

Kbaknife, that's the problem with my setup (and I suspect many others).  How to control the temperature in a very simple forge.  By the way I think I had your handle wrong in one of my posts.  Sorry about that.  I've read just about everything you, Lin, and others have posted on this forum about knife making and have learned a lot from it.  But for a really simple setup like mine, what is a good way to accurately judge the temperature?  Or is there a way?

I'm planning on building a little better "forge" from an old grill I have in the future.  When I can find time.  Clay lining it.  I've been reading up on using a thermocouple with a volt meter to get the temperature.  I'm hoping to get something like this worked out before the end of summer.  But again, time and money are holding me back.  I figured if I can get a setup like this made I can do a little experimentation with fuels and air flow and maybe get it set up to control the temperature much better than I am now.

I don't know.  I'm probably trying to make something simple that is in reality very complicated.  Would a different steel be a better choice?  10xx steels (1080 maybe)?  

Thanks again.  It's really nice to have a place like this to ask questions and get answers from the pros.  I learn something new everytime I get on here.

Aaron

[Jeremy]

1080 steel is very hard to screw up.  You can make a nice knife with O1 with a very simple setup, but it takes more control or a whole lot of luck to get the most out of that steel.  Trying to do a long soak time with anything other than a temperature controlled propane forge or oven would be very difficult.

Re-read Lin's first post.  For the vast majority of hobby knife makers the shady-tree method works well and there's no real reason for the added expense of more equipment.  I've talked to a fair number fo JS and MS knifesmiths now that don't differ from my simple set up very much (OK, so many of them have a power hammer).  

Without exception though, they've done their homework and taken the time to test their methods.  They know the limits of what they can do with the tools at hand.  When I started out a few years ago I read everything I could get my hands on, 'pestered' a few bladesmiths and picked the brains of a couple of guys in the tooling industry who make their living by working and treating steel to very exact specifications.  THEN I played around until I found something that worked and tried to find the limits of my heat treating methods.

[kbaknife]

Aaron, Jeremy and Lin's advice is superb.
Probably the most difficult task we have is to dovetail our expectations and materials to our capabilities and our resources.
If all you have is a coal/charcoal forge, I would suggest not using steel that benefits mostly from long soak times that you can't control.
It might be easier to use such steels as 1080/1084 where about all you have to do is get them non-magnetic and quench in something that will result in martensite.
The more complex steels with higher alloy have requirements that exceed the simple shade tree techniques.
Fun - ain't it?

[ALW]

Thanks again for the help guys.  Hope I didn't come off like I was looking for a simple, no fail way do make a top end knife with little effort.  I'm just trying narrow down what works best and not waste time on something that doesn't show good results.  Like I said I still have some O1 left so I'll do a little more experimenting and see what I can come up with.

I think I may try the 1080 or 1084 steel next, but it seems that some places don't carry it and just about everyone carries the O1.  I'll have to look a little more.  I'll let you know how the next ones come out.

Aaron