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Metal hardening
- Thread starter blacksmithden
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Viscosity. Trans fluid is roughly 5-7 weight oil and that's what you need for a rapid but controlled quench. Heavy motor oil would quench too slowly. Water quenches the quickest provided you add a enough salt to raise the boiling point considerably. Only certain metals can tolerate the extremely rapid quench from water. BTW: I would never recommend using automotive drain oil as it contains a lot of gasoline. The flash point of oil is right at the borderline of the metal temperature and sometimes you get surface flame when using ATF. The gasoline in used motor oil would go up in flames the instant the part hits it -and now you got 2 gallons of burning oil to deal with -and possibly some singed skin.
BTW: When quenchant boils, the vapor bubbles contain super-heated steam and they cling to the part thus, the part is shielded from making contact with the fluid in the tank and the heat cannot be carried away at the proper rate. This is why agitation is very necessary when quenching. It keeps the bubbles from clinging to the part.
Ray
BTW: When quenchant boils, the vapor bubbles contain super-heated steam and they cling to the part thus, the part is shielded from making contact with the fluid in the tank and the heat cannot be carried away at the proper rate. This is why agitation is very necessary when quenching. It keeps the bubbles from clinging to the part.
Ray
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When heat treating most any steel, the critical point, that is the temperature that the metal must be raised to harden, is when the metal becomes non magnetic; when coming up in heat, you just keep trying it with a magnet until it is no longer attracted, then one may hold it at that temp. for a time, then quench. One writer said that moisture in the quenching oil is a problem, this is true, and commercial heat treaters regularly replace their quench oil for this reason, it truly does effect the results of their heat treating.
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Folks,
Just want to mention that using a magnet to determine critical temperature is not always correct. In many metals, the Curie temperature (i.e. where it becomes non-magnetic) is not the same as the critical temperature. For example, the Curie temperature for 1045 steel is 1385 F and the critical temperature is 1570. That misses the mark by about 200 degrees and that has a very measurable difference in the outcome. Most of the common metals we work with are like this. -And alloys... Forget it. It's way off. You need a light spectrometer or IR thermometer that reads up into the 1800 or better range.
It's a good rule of thumb for heat treating a non-critical part -but, don't bet the farm on it.
Ray
Just want to mention that using a magnet to determine critical temperature is not always correct. In many metals, the Curie temperature (i.e. where it becomes non-magnetic) is not the same as the critical temperature. For example, the Curie temperature for 1045 steel is 1385 F and the critical temperature is 1570. That misses the mark by about 200 degrees and that has a very measurable difference in the outcome. Most of the common metals we work with are like this. -And alloys... Forget it. It's way off. You need a light spectrometer or IR thermometer that reads up into the 1800 or better range.
It's a good rule of thumb for heat treating a non-critical part -but, don't bet the farm on it.
Ray
I tend to favor peanut oil as a quench. Readily available and not as toxic 
. I have had good luck with it. You could probably use other vegetable oils as well, but peanut oil has a high smoke point as doesn't varnish as easily as corn or soybean.
. I have had good luck with it. You could probably use other vegetable oils as well, but peanut oil has a high smoke point as doesn't varnish as easily as corn or soybean.
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I am a retired toolmaker. First of all,you need to get a good book on tool steels,and not try to rely on the scattered and contradictory information you will get on a forum,from a bunch of guys whose expertise you do not know.
A good all around tool steel for the parts you mentioned is 01. Take a flat nosed punch and stuff any holes in your parts with fine steel wool to stop the risk of the parts cracking where there are holes. The steel wool makes the parts act like they have no holes. If you do not bother to do this,be prepared to spend all day baking a part,only to possibly have it crack when quenched. No one here mentioned the dangers of quenching parts with holes.
Be SURE to quench in the correct medium. We used automatic transmission fluid in the tool making shop. Yes,with larger parts like plane iron blades,it will flame up a bit,but goes out soon. You can use vegetable oil,or peanut oil as suggested. Do not try using water or brine with 01,which is an oil hardening steel.
Brine is good for W1,a water hardening steel. Brine prevents the envelope of steam which can surround the part when it is quenched,causing uneven hardening. It is doubtful with the small parts you intend to make,that steam will be a problem. However,to make a correct brine solution,add ICE CREAM salt,stirring it into solution until a potato will float in the brine. That gives the correct 7% brine solution. I don't know why ice cream salt is best,but it is recommended in good books on tool steels.
Never quench parts in cold water. It will shock the parts too much,and can cause cracking. W1 is THE MOST TREACHEROUS tool steel there is to harden. I recommend you stay with 01 only,and make lots of parts with it until you get experienced. Then,you can branch out. W1 also moves more than any other tool steel,meaning it changes size some. This is not a lot,but if you have close fitting holes,or other close fitting needs,you might find that the part does not quite fit when you are done. 01 is safer.
The safest tool steels are the air hardening ones,like A2. They also last longer as cutting tools. However,they will decarb while heating up to harden,and will develop a soft skin that you do not want. They must at least be snugly wrapped in a stainless steel envelope. The best thing is to harden them in an inert gas filled furnace. Also,they are more critical about hardening temps. I use an electric furnace with an accurate temp. gauge. The ideal heat is within a 25º range,so again,I recommend you stay with 01 until you get experienced.
Springs are best made of 1080,which is a water hardening steel you can buy from Dixie Gun Works. I have made reliable leaf springs from 01,but the alloys in 01 make it a bit tricky for your spring to not break compared to 1080.
You STILL need to get a good book and read it several times.
P.S.: Kasenite is no longer available. A CLOSED crucible with AQUARIUM CHARCOAL will do a better,deeper case hardening anyway. Make sure the crucible is CLOSED. The lid luted on is best,but a heavy lid will do. When the steel is red hot,its pores are open,and will accept carbon. I THINK the slight gas pressure of there being a lid helps drive the CO2 gas into the steel better. There is controversy about the pressure,but in my experience,it definitely helps. Aquarium charcoal is best because it is full of tiny holes that vastly increases the surface area of the charcoal,making more gas.
A good all around tool steel for the parts you mentioned is 01. Take a flat nosed punch and stuff any holes in your parts with fine steel wool to stop the risk of the parts cracking where there are holes. The steel wool makes the parts act like they have no holes. If you do not bother to do this,be prepared to spend all day baking a part,only to possibly have it crack when quenched. No one here mentioned the dangers of quenching parts with holes.
Be SURE to quench in the correct medium. We used automatic transmission fluid in the tool making shop. Yes,with larger parts like plane iron blades,it will flame up a bit,but goes out soon. You can use vegetable oil,or peanut oil as suggested. Do not try using water or brine with 01,which is an oil hardening steel.
Brine is good for W1,a water hardening steel. Brine prevents the envelope of steam which can surround the part when it is quenched,causing uneven hardening. It is doubtful with the small parts you intend to make,that steam will be a problem. However,to make a correct brine solution,add ICE CREAM salt,stirring it into solution until a potato will float in the brine. That gives the correct 7% brine solution. I don't know why ice cream salt is best,but it is recommended in good books on tool steels.
Never quench parts in cold water. It will shock the parts too much,and can cause cracking. W1 is THE MOST TREACHEROUS tool steel there is to harden. I recommend you stay with 01 only,and make lots of parts with it until you get experienced. Then,you can branch out. W1 also moves more than any other tool steel,meaning it changes size some. This is not a lot,but if you have close fitting holes,or other close fitting needs,you might find that the part does not quite fit when you are done. 01 is safer.
The safest tool steels are the air hardening ones,like A2. They also last longer as cutting tools. However,they will decarb while heating up to harden,and will develop a soft skin that you do not want. They must at least be snugly wrapped in a stainless steel envelope. The best thing is to harden them in an inert gas filled furnace. Also,they are more critical about hardening temps. I use an electric furnace with an accurate temp. gauge. The ideal heat is within a 25º range,so again,I recommend you stay with 01 until you get experienced.
Springs are best made of 1080,which is a water hardening steel you can buy from Dixie Gun Works. I have made reliable leaf springs from 01,but the alloys in 01 make it a bit tricky for your spring to not break compared to 1080.
You STILL need to get a good book and read it several times.
P.S.: Kasenite is no longer available. A CLOSED crucible with AQUARIUM CHARCOAL will do a better,deeper case hardening anyway. Make sure the crucible is CLOSED. The lid luted on is best,but a heavy lid will do. When the steel is red hot,its pores are open,and will accept carbon. I THINK the slight gas pressure of there being a lid helps drive the CO2 gas into the steel better. There is controversy about the pressure,but in my experience,it definitely helps. Aquarium charcoal is best because it is full of tiny holes that vastly increases the surface area of the charcoal,making more gas.
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I have thought of that,but you can also easily buy non iodized regular salt. My wife did-and it hardened up in the box!! Told her to NOT do that again!!!
Beyond that,salt is salt,I GUESS. By the way,all this "Sea Salt" crap!! ALL salt started out as sea salt!!!!!
Sometimes it is not possible to separate fact from LORE. But,in my many years in a museum,I am reluctant to dismiss out of hand the lore part,as it sometimes turns out to be the truth for reasons we haven't thought of. But,at the same time,folk lore needs to be tested first hand before it is recommended. Especially with gun parts involved. I can't tell you how many spurious old varnish recipes I tried when I was instrument maker(before I became the toolmaker) in the museum.
Salt in Mexico is apparently ground much finer than our salt,like popcorn salt. I'd like to find some,because it taste saltier than our salt,being ground finer. It presents more taste area to the tongue,and sticks to whatever you are shaking it on to,like French fries. Plus,you end up eating LESS salt as it its saltier. Of course,the scientists have recently proclaimed that SALT IS GOOD FOR YOU. Wish they's make up their minds!!!
Beyond that,salt is salt,I GUESS. By the way,all this "Sea Salt" crap!! ALL salt started out as sea salt!!!!!Sometimes it is not possible to separate fact from LORE. But,in my many years in a museum,I am reluctant to dismiss out of hand the lore part,as it sometimes turns out to be the truth for reasons we haven't thought of. But,at the same time,folk lore needs to be tested first hand before it is recommended. Especially with gun parts involved. I can't tell you how many spurious old varnish recipes I tried when I was instrument maker(before I became the toolmaker) in the museum.
Salt in Mexico is apparently ground much finer than our salt,like popcorn salt. I'd like to find some,because it taste saltier than our salt,being ground finer. It presents more taste area to the tongue,and sticks to whatever you are shaking it on to,like French fries. Plus,you end up eating LESS salt as it its saltier. Of course,the scientists have recently proclaimed that SALT IS GOOD FOR YOU. Wish they's make up their minds!!!
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