Posts posted by kb0fhp
Take a look at Houghton on Quenching - a good little tome that is pretty non-commercial. It will give you the basics. The file size is too big (just over the 2Mb limit). But I can email it to you - email me at email@example.com. Maybe I can get Don to put it in the archives.
Sorry, didn't explain that very well. I get the blade out of the fire and into the oil as fast as humanly possible, but once it's in there I keep moving it slowly downward, into the mass of oil...once it cools a bit, slowly back up and out. I figure that way it's continually being exposed to fresh oil.
I have lots of experience using recycled steels, and blades I've made from files, newer leaf springs, and the like usually harden up real well in canola with this quench method. I'm suspecting that a lot of my problem with these particular wagon springs is a marginal carbon content for oil-quenching, or a heat-sink effect (or both).
You could also try hardening in a polymer quenchant - a couple of percent would be appropriate. It would provide a quench a bit slower than water but faster than oil so you would get the hamon desired. Also as other indicate, the edge is a bit thin - I would thicken it up a bit.
Use of a brine quench is also good - but very fast.
There is a big difference based on whether or not the steel is plain carbon, low alloy, or high alloy. With 1095, even with a good manganese level, you have less than one second to get the steel to cool from the A1 point to below the tip of the cooling curve. With 52100, which is a medium chromium, high carbon alloy, you have just over two seconds to beat the nose of the curve. Another thing is that 77 points of carbon is all that will disolve in iron. Above that the carbon forms cementite crystals, or iron carbide, which will increase hardness and wear resistance. The cementite formation will also exist in the austinized state of iron so it will have formed before you quench and, on cooling, will be segregated on the boundries of the pearlite/bainite or martensite crystals.
Your question is also rather moot because in both cases the steel would be very brittle and not much of a use for anything unless it cooled too slowly to form martinsite. Also, with temperature being much more critical than time when it comes to carbon migration, I doubt that small differences in the rate of cooling between any usable quenchants would have much effect on the amount of carbon trapped in the body centered crystal to produce martensite instead of ferrite. So the answere is yes, you're overthinking things but that's not necessarily a bad thing. You are trying to come to an understanding of what happens with heat treating. Another good book to read on steel metallurgy is "Steel Metallurgy for the Non-Metallurgist" by John Verhoeven. It's not an inexpensive book, unless you want to compare it to other metallurgy texts carried by Amazon, but it's well worth it.
Assuming a low alloy steel (just iron and carbon), you will not see any increase in hardness at all with an identical quench. The hardness obtainable is governed by the carbon content. Above about 0.65%, you reach a point of diminishing returns - very little additional hardness is obtained. See attached graph.
Carbon can be absorbed by the steel - but only at elevated temperatures in the austenitizing range and from a carbonaceous atmosphere - like a controlled atmosphere or packed in carbon. It does not occur during quenching.
You can get a sneak peek of some of the info you want if you follow this link (which was one of the things that got me started on this fool's errand)
publicly available preview portion from published proceedings of the 22nd Heat Treating Society Conference from 2003.
Start on Page 231!
I WANT TO EMPHASIZE -- I HAVE GOTTEN A SMALL AMOUNT OF A FAST COMMERCIAL QUENCHANT FOR A REASONABLE BUT EXPENSIVE PRICE AND I AM GOING TO USE IT IN THE FUTURE BECAUSE IT IS A SAFER AND MORE "KNOWN" COMMODITY!
Kevin - Thanks for citing me. If anyone wants a copy of that paper I can email a pdf of the file.
See attached. Of all the curves on this sheet - I like the Bio-Quench 700 the best: It has virtually no vapor phase; a very fast maximum cooling rate; and a very high nucleate boiling to convection transition temperature.
Been there done that. No body was interested in selling 5-10 galls of a quench oil, not even Houghton. The Castrol appears to work fine.
Sorry - unfortunately, that is one of the problems. However, if you need more, you could contact a local heat treater - they may have some old oil that you may want to try. Glad you found a source. BTW, vegetable oil is good too.
Why is the tube intact if the exothermic reaction was so great?
I do not think a 10% difference in iron content and would have saved it (304stainless vs carbon steel) if that were the reaction.
Surely there would have been a brighter glow and temp spike if there had been a thermite reaction.
I am not into chemistry as much as you are, but it just does not feel right.
That is the only thing that really makes sense. I am not sure what the tube was made of - if it was refractory (like many are) the melting temperature is much higher that of steel. Because of the color of the salt after the "incident" I would suspect it was consumed. I do know that nitrate salts do produce a strong exothermic reaction if heated to typical austenitizing temperatures.
I was hoping you'd see this, Scott. Thanks for posting. I would like to see a comparison of the curves for canola, straight mineral oil, and the two Houghto-Quench oils (K and G?) you recommended earlier. Well, I know you posted the curves for the houghto-quench oils elsewhere, so don't worry about that.
I can do that when I get my laptop back. I am actually going to a conference in Jacksonville FL in two weeks, where they are discussing this very topic. I am interested in seeing the papers. George Totten (a close friend of mine) is giving a historical review paper on vegetable oils for heat treating.
dunno if it helps at all, but I've cleaned my pot out by running a garden hose in the open end while laying on the ground outside for several hours. Got most of it out then just a bit of mechanical agitation. Then one could dry and sandblast i suppose. I"m using Nu Sal by the way. This was all suggested by Kevin Cashen some years ago. Also don't know what it does for your dirt chemistry, or environemnt.
That isn't a real good idea either - unless you spend a long time drying out the furnace. The best way and also the most tedious, is to chip it all out.
Because of the exothermic reaction I really do think that the blade was consumed. Think of it as a type of thermite reaction. You are really very lucky.
Busted. These guys were supposed to be in their own building and were in storage. This was a last minute rush to do this heat treat and here we are. Still I am bewildered at what happened. Nitrates can do this? The low temp salt is all nitrates or nitrites. One recipe is 50/50 sodium nitrate, potassium nitrate. The other chemical was a pink powder with lumps of a white powder. Don't know yet what it really was.
Absolutely nitrates can do that - they have an exothermic reaction that is really impressive. High temperature salts for austenitizing are all chlorides. Martemp salts are nitrates. If it was pink, then it is likely that it was nitrates.
Funny, I was thinking about this very topic a week or so ago...heated canola is a great quench medium for quite a range of steels, but for certain things it would be nice if it were a just a bit faster. I'd love to be able to get more hamon activity, without having to risk total destruction by water quenching. I was thinking of adding kerosene, but I imagine acetone would thin the oil out more. Since both are pretty highly flammable, any experiments will be done with extreme caution!
(Tip for newbies: if you use a metal container with a lid to hold your quench oil, you can snuff out any flare-ups easily by putting the lid on and cutting off the air supply. I use an army-surplus ammo box.)
DO NOT ADD ACETONE OR KEROSENE TO ANY OIL! They will flash early in your face. I was involved with a fire that happened at a major aerospace company because some idiot didnt want to dispose of some solvent. I dont like getting calls from the local Fire Marshall at home at 4 AM because of something stupid. I dont want to see anybody hurt.
Now regarding canola, it is a fast oil with nice properties. I would compare it to a medium to fast oil. It has virtually no vapor phase and a very high break from nucleate boiling to convection. Agitation will make it faster. There are some additives that make it faster, but unfortunately they are proprietary. We sell the only commercial canola quench oil. I would recommend going to a lower viscosity canola if you want faster or use a fast quench oil). I can show cooling curves in a few days if anyone is interested.
A couple of issues - first regarding the salt:
Your furnaces look nice - well put together it appears.
It sounds like you had a great deal of moisture present. Or you had a T/C fail - you should have an excess temperature T/C wired separately to shut off the heating elements in the even of a thermocouple failure. It sounds like you had a considerable amount of nitrate salt present. This can cause a violent exothermic reaction - maybe enough to cause the blade to be consumed. The discoloration of the salt leads me to believe that this is the case. I would really be interested in finding out the other brand of salt used, and its name.
Second, in the first picture, you have a solvent can directly adjacent to the salt bath. There is also a lot of paper and other debris present which is a BIG fire hazard. There are also a lot of aerosal cans and other flammable solvents and similar near to the furnace - not a good idea.
I am glad you are not hurt - or that you didn't lose any major property. It could have been ugly.
Our shop foreman just came in to the office and said “Look at this! Do you want it?”
He had a 9”chunck of the sheet metal press brake die, which broke out because one of the new guys used the wrong parameters, causing the 80 ton press to think that it’s tooling was 1mm shorter than it really was. The die has a 90deg “v” groove (turned @ 45), so the die basically split in half for 9”. Luckily, the piece did NOT shoot out into his chest; it remained in place, (but it could have, and we were very lucky)
What’s really cool is the grain pattern you can see in the steel, and the radial and arc stress patterns visible in the grain. The piece he was bending was about 2” wide, in the center of the 9” chunk, and there is a very visible “rainbow of failure” extending thru the material.
Anyone know what steel they use for press brake tooling? I’m was thinking S7, but it may be medium carbon because we do saw them to length using our regular steel saw.
I re-sized the pics, but kept some of the file sizes big to preserve the detail. If they get deleated or wreck the forum, I apologize, and will try to down-size and re-post in that case.
You can see exactly where the origin of cracking started - at a flaw in the edge midway up the blade. The chevron markings point directly back to the initiation site. It looks to be a steel that has not been carburized but a quench and temper steel. I would suspect that it may be a variety of steels including high carbon 1080 or 5160. I doubt it would be 4340 as it is very expensive. I would lean more toward a 1080 type. A spark test would give you a good clue.
It is a very slow quenchant. The cold temperature won't do a thing. When you immerse the hot blade, you get a very stable insulating vapor blanket and lots of nitrogen as fog. Now, if it were strogly agitated, you would get a much stronger quench - but you would still have a stable insluating blanket. You would need to agitate it at least 1m/s to do any good - and may require more agitation.
Does anybody use or have used Castrol's Iloquench 395 quenching oil. It is supposedly a 9-11 sec oil and appears to be the only "quickish" quenchant available in Australia.
There are a variety of fast quench oils available in Austrailia - look at Houghton K. YOu could probably contact a heat treater to buy some from them or you can try some local sources.
Well fiddle sticks! I should have ordered more. I could have saved $25 by going ahead and getting two buckets at the same time. I thought one would be all I needed. You think I would learn about all that thinking ; )
Thanks both of you for the info.
If you need the salts, you can make them easily. See the recipe at the beginning or google MIL-S-10699. As an alternative, you could also try contacting Houghton customer service.
Hi all, I differentially quenching in water, steels such as 1050, 1070, W1.water temperature usually is between 50-60 º c. and it appears that the sori, then depends on the thickness of the layer of clay placed on the back, if too thin, it sometimes takes sori reverse. I think it depends more on the insulation that we give to the composition of the clay, do you think? greetings, peter
From a simple metallurgist point of view, I suspect that it has to do with the relative growth of the various phases present. Martensite would grow or expand the most, followed by bainite, and then pearlite. It also depends on when transformation starts. I had an interesting problem like this when a manufacturer decided to go from an 8620 carburized gear to a 4320 carburized gear. It was though that the distortion would be less because of the greater hardenability but because of the timing of the transformation the 8620 had much superior distortion (and was the cheaper solution too).
Depends on the alloy. Many of the precipitation hardening steels like PH13-8Mo or 17-4 have delta ferrite at room temperature. It is a problem after welding as the delta ferrite hurts toughness.
Personally for many industrial applications and for control of distortion and residual stress, I happen to prefer a spherodation anneal. Nice fine grain, uniform response to heat treatment and low distortion. I think several people here have tried it and liked it. One of the really nice things is that it removes the forging residual stresses.
If I run across any I'll let you know, but I haven't seen it before. Most of the clay around here goes into brick manufacturing via General Shale, but I have a potter friend who's into local clays and glaze materials, so I'll ask him if he's seen any.
Multiple causes of distortion and warping - all related to non-uniform quenching.
Causes of Distortion-steel.pdf
Apologies for not following up sooner. The results are good. I've quenched about 6 knives so far; made of O1, 5160, and 1080, and 15N20. They have all turned out really well. I've tested them with rope cutting and slicing, hacking two by's, cutting leather, edge flexing, stabbing a board and chipping it out; you know, the usual stuff. The oil has not flamed up yet when doing multiple quenches.
I'm liking it. The same company makes a faster quenching oil. I'm going to go back and get some of it soon just to do some comparisons of the two and try to learn a bit more about quenches and how much difference the "speed" of the oil really does make.
I don't have a hardness tester, but the qualitative tests so far are good. I've not put a blade through a complete ABS test yet but will soon.
The slow oil is essentially a 100 SUS mineral oil with no additives. The second oil is a medium speed oil that gets its speed using an additive (the reason it is darker). There are a variety of quench oils available that would work well for your application. I am a bit biased in my choice but I work for one of the largest suppliers of quench oil in the world.
For information regarding the effect of oils on hardness and similar things - I would suggest reading Houghton on Quenching (I can email you a copy if you want - just send me an email or note firstname.lastname@example.org). There is another reference book which is really excellent called the Handbook of Quench and Quenching Technology by G. Totten. I am working with George now to rewrite that book and update it with the changes that have occurred in the past 20+ years.
Shell Voluta appears to be a straight 100 SUS oil with no additives or magic pixie dust for anti-oxidation resistance or speed improvers (at least that is the way I read the data sheet). I need to look regarding McMaster Carr.
What I have been up to lately
in Metallurgy and other enigmas
Typically the gears are forged then machined. They are then austenitized and caburized for a case of 0.18 to 0.25 inches deep. The cycle takes up to 7 days. The parts are then quenched and tempered. Distortion is an issue - that is why they take care with the type of agitation and racking. Usually they are ground slightly after tempering - but it is kept to a minimum because it is so expensive. The case is martensitic with a pearlitic core.