H11 hot work tool steel, heat treatment
H11 hot work tool steel, heat treatment
(OP)
I have compared data sheets from several suppliers and the heat treatment temperatures differ.
I have a 4500lb extrusion shell that was inadvertantly left in a gas oven with a faulty controller. The setpoint was set at 960F but it climbed to 1400f and soaked for @12 hours. Some data sheets say 1400F is the midrange for annealing, others say 1550F+.
So my questions are as follows:
1. Is it annealled
2. If it is annealled, could I try a 2 stage temper without hardening.
3. What is the risk if I do nothing.(Material is subject to axial and radial forces)
Thanks in advance
I have a 4500lb extrusion shell that was inadvertantly left in a gas oven with a faulty controller. The setpoint was set at 960F but it climbed to 1400f and soaked for @12 hours. Some data sheets say 1400F is the midrange for annealing, others say 1550F+.
So my questions are as follows:
1. Is it annealled
2. If it is annealled, could I try a 2 stage temper without hardening.
3. What is the risk if I do nothing.(Material is subject to axial and radial forces)
Thanks in advance





RE: H11 hot work tool steel, heat treatment
RE: H11 hot work tool steel, heat treatment
RE: H11 hot work tool steel, heat treatment
I'm assuming the annealing operation took place after the extrusion operation. Are you sure the 1400F soak wasn't intentional? With large parts like yours uneven heating can occur, which can cause warping/cracking.
That being said:
- 1400F, 12 hrs should be enough to recover any cold work. In addition, the temperature is below the austenitizing temperature so you should also get a tempering effect
- Sure you could do a 2-stage temper, but don't go above the austenitizing temperature.
- Have you tried to do any non-destructive testing such as xray diffraction to see what you have?
Metalhead
RE: H11 hot work tool steel, heat treatment
If you need information regarding tempering characteristics, the tempering curve for modified H11 can be accessed in this link:
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Maui
www.EngineeringMetallurgy.com
RE: H11 hot work tool steel, heat treatment
RE: H11 hot work tool steel, heat treatment
Maui
www.EngineeringMetallurgy.com
RE: H11 hot work tool steel, heat treatment
RE: H11 hot work tool steel, heat treatment
As far as how quickly it cooled from 1400F to 1200F I dont know, this happened over a weekend, sods law, and was simply removed from the oven and allowed to cool.
I am waiting to hear from the machine shop where the shell is as far as hardness. Cutting a sample would be difficult as it could potentially compromise the integrity of the shell, and any other testing would be limited (Equipment / resources)
Just for clarification, if the hardness isnt too soft, could I attempt the 2 stage tempering? Reason why I ask this is, our gas oven cannot reach temperature required for hardening (Preheat 1450F, High heat 1825F)
RE: H11 hot work tool steel, heat treatment
Can you not send the part out to be properly heat treated to spec? What condition do you need the material in?
From what I gather is that you have a H11 shell which was extruded 40 years ago. Did you personally do the heat treating or was this immediately following extrusion? A hot extruded material should have very little cold work. The hot extruded micros that I've seen are fine equiaxed after several reductions. The fact that you annealed it after at 1400F, 10hr means that no cold work should be present.
Personally I don't think that material has been hardened because the critical temperature was never exceeded. Now if the critical temperature was exceeded during the extrusion process that's a different story, however I've never hot extruded an alloy more than 100F above the annealing temperature, which (in your case) is likely below your critical temperature.
Metalhead
RE: H11 hot work tool steel, heat treatment
RE: H11 hot work tool steel, heat treatment
Bulk hardness will determine. If it is within the acceptable range per specification, I don't see an issue.
RE: H11 hot work tool steel, heat treatment
Maui
www.EngineeringMetallurgy.com
RE: H11 hot work tool steel, heat treatment
Aaron Tanzer
www.lehightesting.com