Annealing, yet still snapping while bending.

Joe Cabaup

Joe Cabaup

Member
Hello all,

I have been having a strange problem lately, I have been having annealed blade snap while bending

Normally when forge a blade using 1084FG, I normalize it, then heat it back up to red and put it in a trash can of vermiculite overnight.

I messed up a grind bad, to the point that I was going to add it to the ever burgeoning sack of failures when I decided to bend it and throw it away. It snapped at about 70 degrees!

Now I thought since it was annealed it shouldn't snap at all. I changed my annealing process to quenching in Parks 50, then temping it to a dull red and then back into the vermiculite.

Another bad grind so into the vise it went.

Snapped at almost 90 degrees!

A little better but still, what gives?

My set up:

Digitally monitored gas forge. Anneal soaking between 1500 and 1700 degrees for 5 minutes. I do check for decalescence while soaking and start the timing then.
 
What did the grain structure look like where it broke? Could you have overheated the stock some in the forging process? I attached a picture with the same stock but the expanded grain was from over heating and very brittle. What one dose your broken knife resemble?
 
I'm a little confused here as to what you are doing. Annealing does not involve quenching. Normally I don't use a critical annealing because it can result in the coursening of the carbides in the steel. I just normalize to relieve stress and shrink grain size.

I think that what might be going on is that you produce marensite with the quench and the following attempt at annealing does not get the steel hot enough to austinize the steel and you still have martensite, albeit low in carbon. I don't know if I would call brittle failure at an approximately 70° bend a failure, especially if there was not differential hardening of the blade.

Doug
 
Brad: the last one has a very fine structure like the one in top. This was the one that I quenched then brought back to a dull red. The one which just went into the vermiculite look more like the one in the bottom but just a little finer.

Doug: some smiths on this board do quench then "temper" the steel in the forge until it barely glows red. I thought I'd try something new. The blades I did this way did grind a little easier, a little too easy on the one I leaned in on too much and cut the plunge past the midpoint.
 
I'm with Doug on this.
Lose the quench all together if you're going for an anneal. I just give the blank a final subcritical heat and leave it in the forge overnite to cool with the forge. You're going to heat the blade again for presumably normalization and a quench, why add un-needed steps to the process ?

Rudy
 
I think what they are trying, from what you describe, to do is a sub critical anneal which will refine the the carbide structure, also known as spherodizing. The problem is that it's going to be hit and miss, probably more miss, without a regulated heat source. You really need a kiln/heat treating oven to do it right because the steel needs to be soaked at a subcritical point, just under 1400 degrees. for maybe up to a half hour and then cooled slowly. Watching the color of the steel is too inaccurate to do this, you need a pyrometer.

I know that people want to use the techniques that the big boys do but to do it you need the tools that the big boys have, as I learned with my experiments austenpering 52100. You really need to match the steel and techniques that you use to the equipment that you have to consistently put out a good product. There are people out there who try to approximate a technique that they are at best approximating and claim to achieve it without the testing that is needed to support their claims. Some even claim that they do a test to prove that they are right even though the instruments that they use can't test for it.

Doug
 
I'm going to defer to these guys who have more experience than me, but I think 1700deg is a bit too hot for normalizing.
 
Rudy Joly said:
I'm with Doug on this.
Lose the quench all together if you're going for an anneal. I just give the blank a final subcritical heat and leave it in the forge overnite to cool with the forge. You're going to heat the blade again for presumably normalization and a quench, why add un-needed steps to the process ?

Rudy
Click to expand...

I did this for ages with good results. I went back into the shop and found an old blade which I left in the forge overnight and bent the tang back and forth twice until it fatigued and tore.

I was trying to find a better method of annealing in order to make the steel even softer. I think until I vet my heat great oven I will go back to "forge cooling" annealing.

I will also dial down the forge to a 1500 degree max for 1084. That will mean a little more hammering.
 
Let the steel go down to under 1400° if you are tying to come to maximum softness or you will be doing a critical anneal which can cause clumping of the carbides and that can cause problems with drilling. The reason that you might feel that you're getting the softness that you want with that technique is that the pearletic steel is still produced. Why don't you try a side by side test. Also I'm not sure what you mean by reducing the forge down to 1500° and taking a little more time in forging. I know that there are people who do use a sub critical heat to forge at but you shouldn't have to go to that extreme. You can correct any grain growth with triple normalization.

Doug
 
Brad, you are correct 1700° is a little hot for normalization but not too bad unless you are giving it a long soak. I've go 1600°, 1500°, and 1450° Tempilstikss to try out to judge the normalizaton temperatures this year. I think that I need to make up my mind whether or not I want to stick with 9260 or Aldo's 1084 and place an order.

Doug
 
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