Flex after heat treat

D

DirtyDusty

Joined
Feb 1, 2013
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i have been reading through old threads about heat treating 1084. I checked New Jersey steel baron, but they where out of stock. So, I ordered some off eBay. It was listed as .125 1084 steel. I ground out a knife, and then tried to heat treat it. I am using a 2 brick forge with a propane torch blowing through a hole on the side. I heated it up until it was non magnetic, then gave it another minute. Quenched in peanut oil.

Tried a file and it dig in, so I sanded down a little bit and it still dug in. Repeated the heat treat again, same results. Tried quenching in water, still not hard. The metal is still soft enough I can flex it with my hands. Do you think it is my process or could I have gotten some mystery steel?
 
Under hardening comes from not enough heat or too much heat. When there us not enough heat, too few carbides dissolve to put enough carbon into solution to make it hard. Too much heat and a large amount of retained austenite forms, which is soft.

It is possible that you did not soak at temperature long enough.

Hoss
 
I have been experimenting with 1084 alot lately. If it is 1/8 stock and you can bend it easily by hand that seems wrong or you are WAY stronger than me. I have found that vegtable oils dont fully harden but still pass a file test. Water should for sure harden it. With water i measure 65 HRC after my quench. I would suspect your steel is not legit.
 
When you say flex do you mean it stays bent? Because I hope you know that heat treat does not change how easy it is to flex a steel. A hard blade is not more ridged the a soft blade. Also you might have to remove a lot of steel to get to the hard layer. Use a file on the edge and file till you hit hard steel.
 
JTknives said:
When you say flex do you mean it stays bent? Because I hope you know that heat treat does not change how easy it is to flex a steel. A hard blade is not more ridged the a soft blade. Also you might have to remove a lot of steel to get to the hard layer. Use a file on the edge and file till you hit hard steel.
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The hard blade and soft blade having the same resistance to bending thingy. I have seen this around here a few times. To my knowledge that isn't a absolute . I could be wrong but according to my understanding a change of compression strength or tensile strength should have a effect on resistance to bending . I can understand that if it's the same material that effect could be small. If I'm wrong please explain . I'm not trying to start something lol, but I would really like to know. My only knowledge of this comes from making bows and it seems to fly in the face of what I learned there.
 
You're bending .125 stock by hand? How long is the blade? Unless you have green skin and say things like "hulk smash" a lot, I think there is a issue with the steel.
 
Ok let’s use an example. Take 2 strips of 1” wide 1084 that is 1/8” thick. Clamp it to the edge of a bench with say 1ft hanging over the edge. The only thing different between these 2 strips is one is heat treated and the other is not. Then hang 5lbs on the end. Both bars will flex the exact same amount. The only difffrence will be seen if you increase the hanging weight. You will get to a point where the annealed steel will reach a weight where it will stay bent and won’t spring back. But that same weight will not permanently bend the heat treated strip. This is called yeald strength, heat treating increases the yeald strength of steel. It raises the PSI number of the steel where it starts to plasticity deform. The harder the steel the higher the yeald strength and the closer it gets to the tensile strength. Once you hit or exceed the tensile strength psi you snap the blade off. This is why we temper blades. The way I think of it is tempering increases the gap between the yeald and tensile strength. This way we hit the yeald point not the ultimate tensile strength zone.
 
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JTknives said:
Ok let’s use an example. Take 2 strips of 1” wide 1084 that is 1/8” thick. Clamp it to the edge of a bench with say 1ft hanging over the edge. The only thing different between these 2 strips is one is heat treated and the other is not. Then hang 5lbs on the end. Both bars will flex the exact same amount. The only difffrence will be seen if you increase the hanging weight. You will get to a point where the annealed steel will reach a weight where it will stay bent and won’t spring back. But that same weight will not permanently bend the heat treated strip. This is called yeald strength, heat treating increases the yeald strength of steel. It raises the PSI number of the steel where it starts to plasticity deform. The harder the steel the higher the yeald strength and the closer it gets to the tensile strength. Once you hit or exceed the tensile strength psi you snap the blade off. This is why we temper blades. The way I think of it is tempering increases the gap between the yeald and tensile strength. This way we hit the yeald point not the ultimate tensile strength zone.
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This mean under elastic region all steel will has the same rigidity? from 304 to hardened 68HRC maxamet?

From my understanding heat treat do shift the point of yield strength significantly that will effect the "flex" in common perception. I can easily bend the spheroidized annealed steel by hand but it will be much more difiicult doing the same if piece was heat treated.
 
I think that maybe we are talking about different things. I know at least for wood things that affect it's compression and tension strength will affect its stiffness. It seems odd that the same would not be true with other materials .
 
When I say I flexed it, it wasn’t a lot, but I could look down the spine and see deflection. I was under the impression that after the quench, the steel would be real hard and brittle, until it was tempered. But that’s why I am here asking, I am new to this.
 
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As a retired mechanical engineer, I can tell you with all confidence that hardening steel does not change the stiffness. Only altering its thickness or shape can make that happen. No exceptions at all.
Randy
 
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