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Recipe for heat treating BG 42
- Thread starter KenOnion
- Start date
Rob Simonich
Big Bear
- Joined
- Oct 3, 1998
- Messages
- 2,294
Ken, e-mail me your fax number and I will fax Latrobes instruction sheet. But here is the short form.....
Preheat 1500 deg far
Austenitize at 2050 deg far for 30 min minimum
Oil quench to room temp or salt quench at 1050 then air cool (I press quench)
Refrigerate at -100 deg far. (dont say how long but I always snap temper before the refrigeration cycle, then leave in dry ice or LN for several hours.
Double temper at 975 far for 2 hours each cycle.
D-2
Preheat 1100 to 1250, equalize . Heat to 1400 to 1450, equalize.
Heat to 1825 to 1875, (1850) and hold 30 to 45 min at temp.
Air quench or press quench to 150. Snap temper and refrigerate if you like, then double temper at 500 for a 60 rc or so.
Preheat 1500 deg far
Austenitize at 2050 deg far for 30 min minimum
Oil quench to room temp or salt quench at 1050 then air cool (I press quench)
Refrigerate at -100 deg far. (dont say how long but I always snap temper before the refrigeration cycle, then leave in dry ice or LN for several hours.
Double temper at 975 far for 2 hours each cycle.
D-2
Preheat 1100 to 1250, equalize . Heat to 1400 to 1450, equalize.
Heat to 1825 to 1875, (1850) and hold 30 to 45 min at temp.
Air quench or press quench to 150. Snap temper and refrigerate if you like, then double temper at 500 for a 60 rc or so.
Rob Simonich
Big Bear
- Joined
- Oct 3, 1998
- Messages
- 2,294
Welcome Ken.
Sabre, my definition of a snap temper is a quick temper before sub zero quench. (Maybe Paul Bos has a different definition, how about it Paul)?
Sabre, my definition of a snap temper is a quick temper before sub zero quench. (Maybe Paul Bos has a different definition, how about it Paul)?
Rob: You are right, A snap temper is usally done on a hardend blank @ about 350 deg. F. before going in to the sub- zero range. I do this on all tool steels, But on the stainlesses I go right from hardining in to the cryo. treatment.I take it down slowley though. Also if you dont want to temper right away you can do a snap temper to holt it. Paul.
- Joined
- Jan 27, 2000
- Messages
- 615
This thread couldn't have come at a better time. I primarily forge carbon steels, but so as to not put limitations on myself I do occasionally use stock removal and air hardening steels.
I am about to do some stock removal blades in D2. Rob, I notice that you prescribe a two stage ramp for equalization. Is there any particular hold time between these two heatings?
Also, I have never dabbled with cryo and don't have access to a LN dewar. I did however, locate a source within a mile of my house for dry ice.
I'm wondering about containment. I assume a sealed container would leave room for disaster since generated gasses would have no way to escape. I also assume that an open container would not hold the temperature for the necessary time. Could you shed some light on this as well?
I've directed this to Rob because he provided the info, but if Paul or anyone else familiar with these processes wants to chime in, all feedback is welcome and appreciated.
I am about to do some stock removal blades in D2. Rob, I notice that you prescribe a two stage ramp for equalization. Is there any particular hold time between these two heatings?
Also, I have never dabbled with cryo and don't have access to a LN dewar. I did however, locate a source within a mile of my house for dry ice.
I'm wondering about containment. I assume a sealed container would leave room for disaster since generated gasses would have no way to escape. I also assume that an open container would not hold the temperature for the necessary time. Could you shed some light on this as well?
I've directed this to Rob because he provided the info, but if Paul or anyone else familiar with these processes wants to chime in, all feedback is welcome and appreciated.
Snap tempering I done in the range of 300-350F for about 30 minutes, and relieves stress and sets up the microstructure for the deep freeze. An alternative is to perform one, full temper cycle before cryo. Research has been done that shows that going right into cryo without a temper of some sort can cause large grains-a slow deep freeze may help this-I'm not sure.
Doing the temper (snap or full) IMMEDIATELY when the blades are still quite warm is key
As for safety with liquid nitrogen, it's not a problem as long as you don't touch it. There is no danger of explosion, as N2 is an inert gas. Air is 78% N2, and as long as you don't cryo inside a plastic bag (that is, you, the tank and the blades in a sealed bag!), you won't be harmed in the least. Pre-freezing the blades in your freezer will help to reduce the amount of N2 that boils off when you immerse them. Immerse point first so everything cools evenly.
About 6 hours is minimal time, but I always go the full 24.
Doing the temper (snap or full) IMMEDIATELY when the blades are still quite warm is key
As for safety with liquid nitrogen, it's not a problem as long as you don't touch it. There is no danger of explosion, as N2 is an inert gas. Air is 78% N2, and as long as you don't cryo inside a plastic bag (that is, you, the tank and the blades in a sealed bag!), you won't be harmed in the least. Pre-freezing the blades in your freezer will help to reduce the amount of N2 that boils off when you immerse them. Immerse point first so everything cools evenly.
About 6 hours is minimal time, but I always go the full 24.
Rob Simonich
Big Bear
- Joined
- Oct 3, 1998
- Messages
- 2,294
Paul and RJ have filled in the blanks quite nicely!
primos, There isnt a hold time between the first 2 ramps, rather holding at each perscribed temperature until the steel equalizes, which should be a minimum of 10 to 15 minutes in my best estimation with my equiptment. RJ covered the LN, and for dry ice I just use a beat up beer cooler that seals up tight and put the dry ice in a cloth bag and powder it with a rawhide hammer, then pack it around the blades and leave for usually overnight. Also, I usually dry ice before immersing in LN to avoid thermal shock. Paul has the real deal for Cryo, controllable!
primos, There isnt a hold time between the first 2 ramps, rather holding at each perscribed temperature until the steel equalizes, which should be a minimum of 10 to 15 minutes in my best estimation with my equiptment. RJ covered the LN, and for dry ice I just use a beat up beer cooler that seals up tight and put the dry ice in a cloth bag and powder it with a rawhide hammer, then pack it around the blades and leave for usually overnight. Also, I usually dry ice before immersing in LN to avoid thermal shock. Paul has the real deal for Cryo, controllable!
- Joined
- Jan 27, 2000
- Messages
- 615
RJ and Rob,
Thanks for the info. I should have been more specific about what I was considering. I was thinking about trying an old method I read about using dry ice and acetone. Unfortunately the old articles I read didn't provide any specifics about the container. They just warned that this mixture was dangerous.
Rob, if straight dry ice in a sealed container brings you satisfactory results, then I'll go that route.
-Thanks again-
Thanks for the info. I should have been more specific about what I was considering. I was thinking about trying an old method I read about using dry ice and acetone. Unfortunately the old articles I read didn't provide any specifics about the container. They just warned that this mixture was dangerous.
Rob, if straight dry ice in a sealed container brings you satisfactory results, then I'll go that route.
-Thanks again-
- Joined
- May 26, 2000
- Messages
- 1,922
Guys, what is meant by "press quench"?
~~~~~~~~~~~~~~~~
A comment on pure Nitrogen.
I work in the Petrochem industry, and we often have nitrogen purges on vessels and tanks for various reasons, e.g. in prep for doing maintenance. A pure nitrogen atmosphere presents personnel safety risks. If a maintenance worker goes into a pure Nitrogen atmosphere, and they get a big breath of the stuff, they can literally just keel over and die. One just did, across the river from where I work. Nitrogen is of course an odorless and tasteless substance for we humanoids... and so presents a real threat in high concentrations since you get very little or zero warning.
Dry air is, by volume, 78.09% Nitrogen, 20.95% Oxygen, 0.93% Argon, 0.03% CO2, 0.1% Hydrogen, and other trace stuff (Neon, Helium, Krypton, Xenon, Nitrous Oxide, Ozone=O3).
I used to always think "Hey, pure Nitrogen ... hell, I breathe 78% Nitrogen and 21% Oxygen all day, every day. If I got a big breath of Nitrogen, or Oxygen depleted "air", I'll probably just get light headed, I'll realize what's going on, exit this area quickly, and quickly get O2 pumped back into my blood by breathing deeply once out of the area. This would be true for Oxygen depleted "air"... but for pure Nitrogen? Read on ...
I found out something VERY sobering the other day. This info came from an Industrial Hygienist in a report from this most recent incident investigation into why this guy died of N2 asphyxiation.
It is not necessary for nitrogen to displace all of the 21% of oxygen normally found in the air in order to cause harm to people. OSHA requires that oxygen levels be maintained at or above 19.5% in order to prevent injury to workers.
Here is a quote According to the Compressed Gas Association:
exposure to atmospheres containing 8-10 percent or less oxygen will bring about unconsciousness without warning and so quickly that the individuals cannot help or protect themselves.
"Exposure to an atmosphere containing 6-8 percent oxygen can be fatal in as little as 6 minutes. Exposure to an atmosphere containing 4-6 percent oxygen can result in a coma in 40 seconds and subsequent
death."
Ah, 40 seconds you say ... that'll be enough time ... that's what I used to think too.
But if we extend this to pure Nitrogen, we find one of those "here's the rub" awshits:
Apparently, the human breathing response is controlled by the CO2 buildup in your lungs. As long as you have CO2 in your lungs, your brain gets a signal to exhale, inhale, etc. CO2 is of course the byproduct of metabolism, and something very natural in the ingress, absorption of Oxygen from the air, exchange of CO2 out of the lungs, and exhale of air.
So, amazingly, if you get one very big deep breath of pure Nitrogen, or a couple of breaths of 98-99% pure Nitrogen, you can displace all of the CO2 in your lungs. And then the brain gets no signal to exhale. Your breathing stops, cold. Frozen. Paralyzed. You can literally drop in your tracks, unable to take another breath to free your lungs of the N2 and get another gulp of air. This totally popped my belief that "Hey, I'll get lightheaded, and move away and get a breath".
So, not to be alarmist...as working with liquid N2 is of course going to require some other cryogenic safety precautions to be observed, but don't ever get your head into a place that could be full of pure Nitrogen! It could be a sudden end.
And I'm guessing you'd be lying there, totally aware of the fact your breathing was frozen, kind of drowning in thin air, for a about 20-30 seconds or more until you lost consciousness.
Here is a link to the incident report FYI (requires Adobe Acrobat reader, a free download from adobe.com):
http://www.chemsafety.gov/reports/1998/union_carbide/98005_rpt.pdf
~~~~~~~~~~~~~~~~
A comment on pure Nitrogen.
I work in the Petrochem industry, and we often have nitrogen purges on vessels and tanks for various reasons, e.g. in prep for doing maintenance. A pure nitrogen atmosphere presents personnel safety risks. If a maintenance worker goes into a pure Nitrogen atmosphere, and they get a big breath of the stuff, they can literally just keel over and die. One just did, across the river from where I work. Nitrogen is of course an odorless and tasteless substance for we humanoids... and so presents a real threat in high concentrations since you get very little or zero warning.
Dry air is, by volume, 78.09% Nitrogen, 20.95% Oxygen, 0.93% Argon, 0.03% CO2, 0.1% Hydrogen, and other trace stuff (Neon, Helium, Krypton, Xenon, Nitrous Oxide, Ozone=O3).
I used to always think "Hey, pure Nitrogen ... hell, I breathe 78% Nitrogen and 21% Oxygen all day, every day. If I got a big breath of Nitrogen, or Oxygen depleted "air", I'll probably just get light headed, I'll realize what's going on, exit this area quickly, and quickly get O2 pumped back into my blood by breathing deeply once out of the area. This would be true for Oxygen depleted "air"... but for pure Nitrogen? Read on ...
I found out something VERY sobering the other day. This info came from an Industrial Hygienist in a report from this most recent incident investigation into why this guy died of N2 asphyxiation.
It is not necessary for nitrogen to displace all of the 21% of oxygen normally found in the air in order to cause harm to people. OSHA requires that oxygen levels be maintained at or above 19.5% in order to prevent injury to workers.
Here is a quote According to the Compressed Gas Association:
exposure to atmospheres containing 8-10 percent or less oxygen will bring about unconsciousness without warning and so quickly that the individuals cannot help or protect themselves.
"Exposure to an atmosphere containing 6-8 percent oxygen can be fatal in as little as 6 minutes. Exposure to an atmosphere containing 4-6 percent oxygen can result in a coma in 40 seconds and subsequent
death."
Ah, 40 seconds you say ... that'll be enough time ... that's what I used to think too.
But if we extend this to pure Nitrogen, we find one of those "here's the rub" awshits:
Apparently, the human breathing response is controlled by the CO2 buildup in your lungs. As long as you have CO2 in your lungs, your brain gets a signal to exhale, inhale, etc. CO2 is of course the byproduct of metabolism, and something very natural in the ingress, absorption of Oxygen from the air, exchange of CO2 out of the lungs, and exhale of air.
So, amazingly, if you get one very big deep breath of pure Nitrogen, or a couple of breaths of 98-99% pure Nitrogen, you can displace all of the CO2 in your lungs. And then the brain gets no signal to exhale. Your breathing stops, cold. Frozen. Paralyzed. You can literally drop in your tracks, unable to take another breath to free your lungs of the N2 and get another gulp of air. This totally popped my belief that "Hey, I'll get lightheaded, and move away and get a breath".
So, not to be alarmist...as working with liquid N2 is of course going to require some other cryogenic safety precautions to be observed, but don't ever get your head into a place that could be full of pure Nitrogen! It could be a sudden end.
And I'm guessing you'd be lying there, totally aware of the fact your breathing was frozen, kind of drowning in thin air, for a about 20-30 seconds or more until you lost consciousness.
Here is a link to the incident report FYI (requires Adobe Acrobat reader, a free download from adobe.com):
http://www.chemsafety.gov/reports/1998/union_carbide/98005_rpt.pdf