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Heat Treating Results...

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Ray C

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All,

Here are some planned test results on heat treating. The texts I'm learning from really stress proper procedure and I decided to verify if the authors are being overly cautious (with good intentions) or if it really makes a difference. Aside from passing along what I'm learning, there's a motvation in me to post this... Specifically, I occasionally hear folks here planning to heat treat a part -and sometimes the intended part is something criticical like a bucket pin or home-made parts for a hoist etc... Worse yet, sometimes the material is not precisely known.

Summary: Propoer procedure makes a difference -and a lot moreso than I imagined!

Three varying length slugs of 1045 were heat treated with an intended Rockwell of 32-C. The slugs were 1.5" diameter with lengths of 1/2", 1" and 1.5" and were fully normalized using proper technique.

Without getting into the details of the procedure, the piece shown should have had a uniform case hardening with about 0.050" depth. Since it's the smallest piece, it should have cooked the fastest and most uniformly. So... I decided to heat the piece at the low end of 1525 and started the clock as soon as the oven reached that temperature (about 1 hour) and cooked it for 30 minutes. In reality, it should have been allowed to stabilize for about 10 minutes before starting the clock and ideal temperature should have been 1550.

After the part was heat treated, the tempering process was done properly and according to the cook book.

Here's what it looks like. The piece was face turned in 0.010" increments and on the 2nd pass the soft chewy center was visible. It didn't even harden down to the desired depth. -And by the way, you've probably seen how cold-rolled steel shows this same pattern and it's proof positive that stresses are present in non-normalized material. The Rockwell tested-out at 27-C but, at the current time, the test apparatus is not verified. I'm using a rebound type and also evaluating some brinell testers. -But before making any serious investments, want to learn more about the merits of each technique.

I heat treated some of the othe parts in proper fashion and they pretty-much produced the desired results. BTW: by peeking at the color of red inside the oven, I sure has hell (pun intended) can't tell the difference in color between 1525 and 1550. Even following the cook-book, I did not achieve uniformity in the other pieces that were done properly. It was pretty close -but no cigar... Need to read/learn/experiment more... I think it's a quenching problems but at this time do not have enough knowledge to analyze the symptoms. I'm pretty sure I'll get a handle on this in the next week or so.

BTW:... somewhere along the line, I'll include some comments about the PID controller. Seems to have some glitches -not the end of the world but minor annoyances.

Ray


Treated Part 30..JPG

Treated Part 30..JPG
 

Tony Wells

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IMO, the penetration method is much more accurate than the bouncing ball. You can get an import machine for around a grand. It will cover several ranges and scales. There are procedures to hardness checking that must be followed also, and if you don't follow them, you won't get accurate results. For the record, the spec you see on off the shelf heat treated material is checked mid-radius on the face of the bar (round stock that is) and any decarb zone has been removed.


How did you accomplish your quench?
 

Ray C

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Brine water brought up to 200F before the dunk as not to let the part drop below 200 for the ensuing tempering. 1550 straight into the brine. Basket bottom container. Used enough quenchant volume to cool from 1550 to 250 in a matter of 15 seconds (approx). -Boiled like heck and I "think" that's the problem -superheated steam all around the part... -but not sure.



IMO, the penetration method is much more accurate than the bouncing ball. You can get an import machine for around a grand. It will cover several ranges and scales. There are procedures to hardness checking that must be followed also, and if you don't follow them, you won't get accurate results. For the record, the spec you see on off the shelf heat treated material is checked mid-radius on the face of the bar (round stock that is) and any decarb zone has been removed.


How did you accomplish your quench?
 

Tony Wells

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Might well be the steam. Can't let the steam stay on the part. Have to keep it agitated as much as possible. Also, the quench medium has to remain at the desire temperature, or within limits. If it heats up too much, you aren't quenching fast enough to ensure grain capture. It's a tricky sort of thing.
 

Ray C

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This takes practice for sure. That's why I decided to experiment with some "bad practices" to convince myself that short-cuts are bad news.

Agitation: I sure as heck could not stop that steam if I wanted to. I think maybe will be limited to certain levels of qualty with brine. Maybe I'll try oil in the future. This is going to have some learning curve...

BTW: Gives me a new appreciation for hot things. Doesn't bother me to be face-to-face with a TIG torch or stick. The heat is small and focused. Large volumes of super-heated sapce---things glowing red and you can't even tell where all the red color is coming from. -Different can of worms than anything I've done before. Fun times... BTW: Oven box doing nicely!


Hardness Testers: Still evaluating needs while reading-up on the matter.

Ray


Might well be the steam. Can't let the steam stay on the part. Have to keep it agitated as much as possible. Also, the quench medium has to remain at the desire temperature, or within limits. If it heats up too much, you aren't quenching fast enough to ensure grain capture. It's a tricky sort of thing.
 

DMS

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I have done a bit of HT, but never on anything that thick (the thickest I have worked with is 3/4"). Mostly I use W1 (it's a plain carbon steel, and should behave pretty similarly to 1045). I typically quench in plain water. From what I have read, plain carbon steels won't harden through in thick pieces, though getting a good soak will improve this. Temperature when hardening plain carbon steels is not that critical with the exception that you want to get it up past the austenizing temperature, and you don't want to get it too hot, too long, or you will de-carburize the surface, and it will be soft. Tempering temperature is more critical if you want to hit the desired hardness. Chromium steels are much more finicky when it comes to hardening, not just with temperature, but with time (heat them too long, and they become grainy, and lose toughness).

As far as the steam causing problems, yes, it does, that is the reason brine is preferred to water in some cases (it keeps the bubbles small, and they tend to cling to the surface less). I remember reading about other additives that people add to their quench to improve things even more, but can't seem to find the info when I look now.

You may get better through hardening with different steels (O1, 5160).
 

jgedde

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Just to set the record straight as the OP didn't specifically say he is case hardening...

W1 is all together different than 1045. W1 is a high carbon steel alloyed with other good stuff. It is inherently hardenable simply by heating and quenching.

1045 is a low carbon steel and will not harden the same way. Additional carbon must be added: charred bone meal, charred leather, charcoal, Kasenit, etc. In other words, case hardening.

I believe the OP is correct. That said, it's relatively easy to get W1 (or O1) how you want it - especially if you know ahead of time how it will react (generally it grows slightly). Case hardening is another matter. I have had mixed results trying to do case hardening myself. The process can be picky and getting a consistent hardening depth is an art form in my opinion.

Even the pros don't always get it right. At work, we have our case hardening and nitriding done outside. A few pieces from every lot are hardness tested and plated/microsectioned for analysis. The results often vary widely.

John

- - - Updated - - -

All,

Here are some planned test results on heat treating. The texts I'm learning from really stress proper procedure and I decided to verify if the authors are being overly cautious (with good intentions) or if it really makes a difference. Aside from passing along what I'm learning, there's a motvation in me to post this... Specifically, I occasionally hear folks here planning to heat treat a part -and sometimes the intended part is something criticical like a bucket pin or home-made parts for a hoist etc... Worse yet, sometimes the material is not precisely known.

Summary: Propoer procedure makes a difference -and a lot moreso than I imagined!

Three varying length slugs of 1045 were heat treated with an intended Rockwell of 32-C. The slugs were 1.5" diameter with lengths of 1/2", 1" and 1.5" and were fully normalized using proper technique.

Without getting into the details of the procedure, the piece shown should have had a uniform case hardening with about 0.050" depth. Since it's the smallest piece, it should have cooked the fastest and most uniformly. So... I decided to heat the piece at the low end of 1525 and started the clock as soon as the oven reached that temperature (about 1 hour) and cooked it for 30 minutes. In reality, it should have been allowed to stabilize for about 10 minutes before starting the clock and ideal temperature should have been 1550.

After the part was heat treated, the tempering process was done properly and according to the cook book.

Here's what it looks like. The piece was face turned in 0.010" increments and on the 2nd pass the soft chewy center was visible. It didn't even harden down to the desired depth. -And by the way, you've probably seen how cold-rolled steel shows this same pattern and it's proof positive that stresses are present in non-normalized material. The Rockwell tested-out at 27-C but, at the current time, the test apparatus is not verified. I'm using a rebound type and also evaluating some brinell testers. -But before making any serious investments, want to learn more about the merits of each technique.

I heat treated some of the othe parts in proper fashion and they pretty-much produced the desired results. BTW: by peeking at the color of red inside the oven, I sure has hell (pun intended) can't tell the difference in color between 1525 and 1550. Even following the cook-book, I did not achieve uniformity in the other pieces that were done properly. It was pretty close -but no cigar... Need to read/learn/experiment more... I think it's a quenching problems but at this time do not have enough knowledge to analyze the symptoms. I'm pretty sure I'll get a handle on this in the next week or so.

BTW:... somewhere along the line, I'll include some comments about the PID controller. Seems to have some glitches -not the end of the world but minor annoyances.

Ray


View attachment 53417
Ray, what are you using for a source of the additional carbon? Kasenit? CO2? Just curious.

John
 

DMS

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1045 is classified as a "medium carbon" steel. It's hardenable (carbon content above the minimum of 0.4%), but just barely. Looking at the specs for W1, you are right, not a great comparison between it and 1045 (it's closer to 1095).

Ray, given that this was your "slapdash" attempt, to see how bad things can go, I am pretty interested to see how your textbook attempt goes.

I found that quench recipe

http://www.anvilfire.com/FAQs/quenchants.htm
 

Ray C

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Yes indeed... 1045 has just enough carbon to do surface hardening but, the real goal was twofold. By properly normalizing (high heat with gradual cool-down) it makes the internal structure uniform and of a structure amenable to strength. In the vernacular, surface hardening seems to imply using the metal's existing carbon whereas case hardening seems to imply using an exterior carbon source to "impregnate" the surface. FWIW: These definitions are by inference of my reading and it's not specifically stated that way...

Thanks for the quench info. I did notice in that writing a reference to someone whose punch shattered upon use. It's not due to the quenchant at all. The books absolutely warn people never to use hardened steel that has not been properly tempered. Even lowly 1045 will have a 100-range RC immediately after hardening. The tempering brings it back down to a usable state. I tried to test my pieces immediately after hardening but, A) they were too hot too handle and B) the time required would have pushed the 1 hour envelope by which the tempering process must begin. It's clearly stated in all the references that tempering of all carbon steel must begin within 1 hour of heat treating and when the part is on the down-slope cooling phase between 150 and 125 degrees (no more, no less). There are ways around this -such as keeping the metal at 450 until the tempering can be done at a convenient time etc... Electron micrographs are shown of what happens when uniform samples violate those rules and the images do not even appear to be the same metal.

BTW: The textbook piece came-out pretty well. It's pretty much destroyed now and looks a lot like the one shown; however, the hardening had a depth of about 30 thou and not (approx) 15 thou like the other. I ripped it on the sides with an endmill with pretty-much the same findings (best I could tell).

Using the rebound hardness tester, I checked some known tooling at 50 and 60 RC and got very close results. Still don't quite know why my piece came out about 6 points lower than expected but, I'm not going to sweat this for now.

One thing I've learned is that solid textbooks on the matter are worth it! I tried for months to read various Internet sources and it's all over the place -somewhere between witchcraft and alchemy. I could not find the same story in two places... This is quite a science actually and now I know why my uncle turned from chemist to metallurgist -and that was back in the 50's when this was groundbreaking stuff.

Ray



1045 is classified as a "medium carbon" steel. It's hardenable (carbon content above the minimum of 0.4%), but just barely. Looking at the specs for W1, you are right, not a great comparison between it and 1045 (it's closer to 1095).

Ray, given that this was your "slapdash" attempt, to see how bad things can go, I am pretty interested to see how your textbook attempt goes.

I found that quench recipe

http://www.anvilfire.com/FAQs/quenchants.htm
 

Tony Wells

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A piece that has the cross section like your samples will have a hardness gradient through the diameter. It's unavoidable. When you quench, the outside cools quickest, but naturally, the heat from the core must transfer outward to the quench media, so quenches slower, yielding softer steel. That's why the mid radius method is really a standard method. The actual measured hardness is greater the closer you get to the OD of the par, and at dead center, it is softer. That's just the way it is. Some people who buy trepanned cores often are misled into thinking that the material is exactly like the bar that is is cored from, but it is invariably softer than the nominal hardness called out for the parent bar. Same chemistry, but different mechanicals. You will see deep grinds (1/4" deep at times) on larger rounds, such as 8" and up, and a portable Brinell tester is chained to the bar or part, and an indention is made under controlled pressure with a known spherical penetrator. The diameter of the impression is measured and a chart guides the hardness comparison.

A bench type Rockwell machine is more suited for the smaller parts hobbyists and small shops are likely to see, and for your size furnace, would be preferred over portable Brinell machine.
 

pdentrem

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Believe it or not we bought one of these, BTW this guy is on crack asking that much. MSC sells one for $1600.

http://www.ebay.com/itm/Wilson-3JR-Regular-Rockwell-Hardness-Tester-B-Scale-C-Scale-Dial-Indicator-/221198368488?pt=LH_DefaultDomain_0&hash=item3380733ee8

For only $100.00! We immediately purchased a 50 to 60 standard and new penetrator for more than that. The machine shop was in receivership and we dove in and scooped what we could get. Left lots of stuff behind as we ran out of money.
Pierre
 

Ray C

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All,

Here's a pretty good read on hardness testing 101: http://www.hegewald-peschke.com/info-bereich/guidelines-to-hardness-testing.html The only thing not covered is electronic/ultrasonic methods.

I've found some pretty good Rockwell units (new production) similar to what Pierre showed in the $700 range and I'm waiting to see if one in-particular does Brinell too. It's unlikely I'll look to eBay as, I have no desire to deal with damaged or kludged-up penetrators -and gosh knows what else goes wrong with them. In half the photos, you can see they're missing some parts. And like Pierre mentioned, people seem to want more for used ones than what new ones are going for.

I'm also digging-up info about the hand-held electronic units but haven't gotten too far with that. Any words of wisdom there?

Today, I worked on the box and started to read the instruction manual on the controller. -Poorly translated. The controller has adjustable parameters on convergence which I'd like to tweak. I also saw some strange behavior when trying to step-down the temperature. Wanted to recreate the situation today but, just ran out of gas and did other reading instead.

Ray
 

Kevlar

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All,

Here are some planned test results on heat treating. The texts I'm learning from really stress proper procedure and I decided to verify if the authors are being overly cautious (with good intentions) or if it really makes a difference. Aside from passing along what I'm learning, there's a motvation in me to post this... Specifically, I occasionally hear folks here planning to heat treat a part -and sometimes the intended part is something criticical like a bucket pin or home-made parts for a hoist etc... Worse yet, sometimes the material is not precisely known.

Summary: Propoer procedure makes a difference -and a lot moreso than I imagined!

Three varying length slugs of 1045 were heat treated with an intended Rockwell of 32-C. The slugs were 1.5" diameter with lengths of 1/2", 1" and 1.5" and were fully normalized using proper technique.

Without getting into the details of the procedure, the piece shown should have had a uniform case hardening with about 0.050" depth. Since it's the smallest piece, it should have cooked the fastest and most uniformly. So... I decided to heat the piece at the low end of 1525 and started the clock as soon as the oven reached that temperature (about 1 hour) and cooked it for 30 minutes. In reality, it should have been allowed to stabilize for about 10 minutes before starting the clock and ideal temperature should have been 1550.

After the part was heat treated, the tempering process was done properly and according to the cook book.

Here's what it looks like. The piece was face turned in 0.010" increments and on the 2nd pass the soft chewy center was visible. It didn't even harden down to the desired depth. -And by the way, you've probably seen how cold-rolled steel shows this same pattern and it's proof positive that stresses are present in non-normalized material. The Rockwell tested-out at 27-C but, at the current time, the test apparatus is not verified. I'm using a rebound type and also evaluating some brinell testers. -But before making any serious investments, want to learn more about the merits of each technique.

I heat treated some of the othe parts in proper fashion and they pretty-much produced the desired results. BTW: by peeking at the color of red inside the oven, I sure has hell (pun intended) can't tell the difference in color between 1525 and 1550. Even following the cook-book, I did not achieve uniformity in the other pieces that were done properly. It was pretty close -but no cigar... Need to read/learn/experiment more... I think it's a quenching problems but at this time do not have enough knowledge to analyze the symptoms. I'm pretty sure I'll get a handle on this in the next week or so.

BTW:... somewhere along the line, I'll include some comments about the PID controller. Seems to have some glitches -not the end of the world but minor annoyances.

Ray


View attachment 53417
i do a lot of heat treating of the knives I make. I think you should increase your soak time in the oven to insure you get the entire piece to the proper tempature. It may also be that you did not quench the part quick enough or the tempature of the quench oil was not warm enough or if using brine there are lots of things that can happen depending on the steel. Using salts to heat treat is a better way to control all the factors but it should only be done with great care and never by a novice without experienced supervision. Very serious injury can result. Be sure to normalize the piece 3 times to remove stress in metal to reduce war page and cracks. Heat uniformly and quench properly in warm quench oil. Once at room tempature put in oven and draw to desired tempature. A last note if you are unsure of initial hardening heat check the steel with a magnet. It will be non magnetic at its criticle state. Hope this helps
 

Ray C

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OK... moving right along here...


I made several parts this weekend requiring a TIG weld with ER80S with final finishing later. Weld caps are hard. It make the best HSS cry like a baby and eats carbide inserts faster than stainless steel. The solution? Normalize! Can't show you the part right now, it's still tapering-down in the oven.

While the oven was fired-up last night, I took a shot at carburizing a different finished part made of 1045 (It's 3.25" dia, 1/2" thick). This was a finished part that I'll have to re-finish and do a rockwell test. The part does not need this level of treatment but, it won't hurt and I'm just experimenting. Anyhow, I sealed the part in stainless foil, shot it up with CO2, cooked it at 1565 for 40 minutes and threw it in brine then, tempered it at 400 for 2 hours. This should give a 50 RC.

Hope it comes through in the picture but the finish right now looks like matte black oxide. It's not dirty at all and doen'st rub-off on your fingers. It should clean-up nice. First I'll sandblast it to see what that looks like and maybe hit it with ceramic on the lathe.

Ray
C02Part.jpg

C02Part.jpg
 
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DMS

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I don't think your case is going to be very deep Ray. The CO2 may help reduce decarburization, but there is not going to be much available carbon to absorb into the surface. I have not tried it myself, but I recall an article in HSM that walked you through the process. IIRC the guy was using a commercial product, but I have heard the old timers used bone meal and oil, packed in a steel container. If I remember, I see if I can find the article when I get home.
 

Ray C

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Yeah, probably right -but it sure looks cool.

One book I have describes many of the modern/useful methods of carburizing and I went into this knowing well I wasn't doing a completely proper job. I was really just normalizing a couple parts and decided to try this at the last minute because the oven was hot. Anyhow, the added CO2 (as you said) probably minimized the decarburization.

I'm still trying to get a handle on quenchant. I increased the salinity and this time, it produced a 1 minute long show of what looked like foaming soda bubbles -but extremely turbulent. Wish I knew what to expect. The book I have that covers 1045 is not "cookbook". It only mentions the possible processes and "what" to do; not, "how to do it" or "what to expect".




I don't think your case is going to be very deep Ray. The CO2 may help reduce decarburization, but there is not going to be much available carbon to absorb into the surface. I have not tried it myself, but I recall an article in HSM that walked you through the process. IIRC the guy was using a commercial product, but I have heard the old timers used bone meal and oil, packed in a steel container. If I remember, I see if I can find the article when I get home.
 

Ray C

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OK, so I tied a "Pack Carburize" technique on a piece of 1045 scrap. It worked very well except that I managed to get surface cracks. The problem with quenchant is resolved and in this case, it worked too well. Oil would have been better in this case. It tests out at 55 RC and is very deep. One side was surface ground and I gave-up at 60 thou since I was only hoping for 50 thou. The other side (shown) was lathed and instantly punished a carbide tip and wouldn't cut.

HT1.JPG

BTW: I made more grinder hubs the other day which are two piece welded. The weld caps usually beat-up carbide so I normalized the piece first and the whole thing (caps and all) cut like butter. Now that they're shaped, I'll bring them up to 30 RC, do the final surfacing, black oxide them and call it a day.

Next project is to take a piece of tool steel and make a B&S taper reamer (can't find one commercially). I'll try to bring that up to 60+ RC. Still deciding if I should practice on a piece of tool steel first.

Ray

HT1.JPG
 

DMS

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That's pretty awesome Ray. Thanks for keeping us up to date.
 

Ray C

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Thanks for the kind words. Since I have no artistic ability I stick to technical things. The business of heat treating is confusing when you try to glean information in bits and pieces. As I started to do more interesting lathe/mill work, it became apparent you cannot escape some heat treatment processing. Some stuff is just too darn hard to work on unless normalized and then of course, they need to be re-hardened later on. I had other parts changing shape in other places when I milled on them (internall stresses letting go). I tried reading various articles on the "Net" -and ended-up screwing-up parts (fortunately, all things from my personal pet projects).


Anyhow, the 4-5 books I've picked-up in the last several months cost just under 600 bucks with one book in particular costing $350 -and that just covers ferrous metals. And of course, the books that cover Inconel (which is what I'm really after) are even more rare. At the moment, I'm only disussing the things which I'm universally certain about and once I get more practical information, I'll pass it along.

So, you seem interested... Go ahead and ask about the quenchant and what I concocted for pack carburizing.

Ray


That's pretty awesome Ray. Thanks for keeping us up to date.
 

MikeWi

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So, you seem interested... Go ahead and ask about the quenchant and what I concocted for pack carburizing.
Ray
Hey Ray, tell us about the quenchant and what you concocted for pack carburizing.
 

Ray C

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Well... how fortuitous that you ask...


Quenchant: For now, using baking soda and water. You must use what's correct for the metal. 1045 likes water cooling. What the books say about sinking potato peels -that's just a starting point. I test the solution by heating (with oxy/propane torch, simple mapp or propane torch is not hot enough) a 1/4" thick piece of metal until it's red/orange (color is important. Cherry red is cold. Orange, now you're talking) and dunking it until it does not boil with big bubbles but rather, fine "soda" or "carbinated water" bubbles. If the bubbles are too big, the hardness just won't be there in the finished piece. Add bi-carb soda until the desired bubbles are obtained when quenching a test part. Why bi-carb? It's a salt and it's cheap.

The water should start-out room temperature and there should be sufficient volume so the terminal temperature of the part and water is 150 degrees. I'm in the process now of writing the formulas to know how much water to start with to accomplish this. BTW: The books don't tell you this but it's easy inference if you see the picture of what's going on. At the very least, start-out with enough water and pull the part when it hits 150 (which is right at the threshold of being able to handle by hand). A rapid and smooth transition to 150 is the key. These little subtle points are what make a difference between something that comes out 30 RC when you intended 40 etc.


Pack Carburizing for low and mid carbon steel: So far, 95% crushed charcoal and 5% (by weight) potassium nitrate. Ground-up and crushed together. (Don't add any sulfur unless you plan to make gunpowder). I'm still tweaking this and may up the potassium to 10%. The potassium becomes solute with the charcoal at/around 500. The combination of the two produce a large amount of CO2 when temps hit 1300. This carries the carbon right into the metal as it starts to hit austentizing state. Of course, I'm wrapping in tool foil. The aftermath is not messy at all. Just some grey powder and scale afterward. It's all incenerated and the carbon is gone into the metal.


Ray


Hey Ray, tell us about the quenchant and what you concocted for pack carburizing.
 

woodrowm

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Good afternoon - Hey, very interesting thread, would you mind sharing some info about your oven set up. Such as make, model, where did you get it or is it home made, is it inside your shop or outside ect. Any info would be helpful.

Thanks,
Woodrow
 

Ray C

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Hi Woodrow,

It's all documented here with the juicy stuff starting at post #26 of this thread: http://www.hobby-machinist.com/showthread.php/9929-Heat-Treat-Oven/page2?highlight=heat+treat+oven


Oh, BTW: It's inside my shop. When in operation it's only warm to the touch -and barely that. It's when you open the door things get hot.


Ray




Good afternoon - Hey, very interesting thread, would you mind sharing some info about your oven set up. Such as make, model, where did you get it or is it home made, is it inside your shop or outside ect. Any info would be helpful.

Thanks,
Woodrow
 

Kevlar

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I have a paragon inside the shop and I have a co2 line with a regulated flow going in to keep from having to wrap my parts in stainless foil and I can polish the part up beforehand without much clean up. The shop has a hood vent do to the c02 but the flow is slight due to thermal expansion. It is a need trick that I picked up on a trip through mike bosses shop before he retired. The guy was a heat treat legend in the industry. Take care all.
 

Ray C

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I'd like to experiment with that some time. Good to know you've done it and get OK results so I at least know I'm not barking up the wrong tree.


Ray


I have a paragon inside the shop and I have a co2 line with a regulated flow going in to keep from having to wrap my parts in stainless foil and I can polish the part up beforehand without much clean up. The shop has a hood vent do to the c02 but the flow is slight due to thermal expansion. It is a need trick that I picked up on a trip through mike bosses shop before he retired. The guy was a heat treat legend in the industry. Take care all.
 

Ray C

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Made many more parts with weld build-up today so the oven was used to normalize them. They're all slow cooling now. While the oven was hot, I hardened a few pieces and tempered to a desired Rockwell of 40 RC. With the tester I'm using now reads 38 RC on the part. I've used the tester on some materials with know hardness of 60 and 62 and it gives results that are almost dead-on. I was shooting for 40 and got 38... For now, I'm OK with that.

Another ingredient (chromium oxide 1%) was added to the pack carburizing mix. I did one part with the chromium oxide and the other w/o it. Here's a few pics along the way. -Amazing how a few grams of a substances changes things so much. Both tested at the same rockwell but the finish felt different even though they were identical parts.

I use Caswell black oxide on a lot of things. The part that had the chromium did not accept the oxide treatment as well as the other part. To be expected I suppose; chromium does not oxidize very much -if any at all. Here are pictures of just the chromium treated part. The other is identical but has a darker tone.

First pic, right out of the oven, quenched and tempered.

OutOfOven.JPG

Second Pic, same piece after a few moments in the sandblaster. -Interesting to see sparks flying around in the sandblast box.

BrushedOff.JPG

Third pic, oxidized but not sealed yet. BTW: The Caswell treatment is a two-part chemistry. First step is to degrease the part and dunk it in the oxidizer then let it air dry. I find that performing that step a second time gives a better finish.

Caswell 1.JPG

Last pic, finished part after sealing and warm-air dried. The second Caswell step is to apply a sealer and let it air dry. It immediately turns black. The sealer smells just like linseed oil -although I don't know if that's what it really is. And for the record, the black oxide does not enhance the hardness of the part. It's just a surface treatment to retard rust. It works very well. A lot of the stuff I make is used on Yachts and most folks here navigate brackish and ocean routes. Nothing has rusted yet.

Caswell 2.JPG

... Looking forward to getting a Rockwell tester and I'd also like to get a Leeb unit as well. It's going to be a few more weeks before I turn enough jobs to get those.


Ray

BrushedOff.JPG Caswell 1.JPG Caswell 2.JPG OutOfOven.JPG
 

cdhknives

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Ray, have you gotten to the point in your reading of studying TTT curves for various steels? They are widely available for simple heat treatable steels and most common tool steels. Once I understood the time and temperature factors concerned with hardening and crystal structure of the steel the procedures really started to make sense...and showed why it is so easy to fail the whole cycle with one tiny shortcut.

I was studying the many MANY conversations (arguments, fights, etc.) on the knifemaking forums and it got me curious enough to read up on it like you seem to be doing. I stick to commercial quench oils (after a brief experiment with ATF) to take that variable out of the equation.

WRT your case hardening, you are essentially changing the medium carbon surface to high carbon, so heat treat to the high carbon. For example:

http://www.cashenblades.com/steel/1080.html

Cracking is VERY common in water/brine quenching high carbon steels. The Japanese swordsmiths made an art out of interrupted quenching simple high carbon steel...another concept you may have read about.:thinking:
 

Ray C

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Hi...

Oh yes, doing lots of reading. All books so far cover TTT within the first section. This is really fascinating stuff and gives me the sense that metal is much more "alive" and has more "personality" (not anthropomorphically speaking) than I ever imagined. Anyhow, like you, I saw many conflicting techniques on the Internet covering the same topic. My uncle was a chemist turned metallurgist but, at the time he was still alive, I did not have the educational background to keep-up with his knowledge. My father was an old school T&D maker and he and my uncle shared lots of information at the family table but, my uncle's words went over my head at the time. In any event, I went straight to the professional publications from the AISI. Cost me a fortune but was cheaper than purchasing the individual chapters in PDF form... -And I have no desire to deal with knucle-headed arguments on Internet groups... What really bugs me is that I think my sister still has some of my uncles books -but she can't find them.


Right now, I'm slowly proceeding -mainly because it's a very time consuming process! I've noticed some things which I haven't been able to find information on... Maybe you know what's going on.

I've noticed that medium carbon steel tends to be slightly magnetic after heat treat quenching. Is this a good or bad sign?

Also, it seems (but I haven't systematically verified) that metal picks-up 1-2 Rockwell about 24 hours after the final treatment steps and cool down to room temperature.

I will look around for some quenching oil. I have seen some cracks here and there. Is it available in reasonable sized quantities? Also, would you mind making recommendations based on the kind of work I do? It's mostly machine parts of 1045 and some 41xx. I make a lot of shafts with flanges that are two-part welded (similar metals) so I need to normalize after weldin, bring to final dimension, then surface harden a little bit.

And finally, I didn't know about differential treating until it was mentioned on another post of yours several weeks ago and of course, I looked it up. LOL... At the moment, I'll just stick to getting uniform treatment...


Ray




Ray, have you gotten to the point in your reading of studying TTT curves for various steels? They are widely available for simple heat treatable steels and most common tool steels. Once I understood the time and temperature factors concerned with hardening and crystal structure of the steel the procedures really started to make sense...and showed why it is so easy to fail the whole cycle with one tiny shortcut.

I was studying the many MANY conversations (arguments, fights, etc.) on the knifemaking forums and it got me curious enough to read up on it like you seem to be doing. I stick to commercial quench oils (after a brief experiment with ATF) to take that variable out of the equation.

WRT your case hardening, you are essentially changing the medium carbon surface to high carbon, so heat treat to the high carbon. For example:

http://www.cashenblades.com/steel/1080.html

Cracking is VERY common in water/brine quenching high carbon steels. The Japanese swordsmiths made an art out of interrupted quenching simple high carbon steel...another concept you may have read about.:thinking:
 

cdhknives

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Look at TTT curves for alloy steels and you will note that the transformation curve may extend to the hours+ range. Some high alloy steels literally do not fully transform at room temperature as well. This is where cryo quenching becomes real. It both speeds and drives to completion the martensite transformation. What I suspect you are seeing is the time factor coming in. It may take a day or so for alloy tool steels like O-1 or 40xx (and maybe even simple 10xx steels with some 'trash' alloying elements...nothing is pure any more) to fully transform and get that final point or 2 of hardness. For really wild steels like some of the particle metallurgy steels or some rare earth alloying elements the cryo quench adds 3-5 points of hardness that would otherwise never appear.

I bought quench oil in gallon quantities from McMaster. They have a fast and slow version, but I don't think their fast is 'fast enough' for 10xx series steels that need to go from 1500F+ down a few hundred degrees in under a second (hence the impossibility of fully hardening them to the core in larger cross sections) to miss the perlite nose of the TTT curve. They are great for 40xx and O1 class steels though. W1 is a water quench steel, hence the W designaiton. O series is oil quench. A series is air quench. (Yeah! Just let it cool in air! Easy!) Many suppliers don't want to mess with individuals and only sell in 55 gallon drum qty. Ugh. If you can find Parks quench oils in 5 gallon size they make a very fast oil (Parks #50 IIRC) supposedly 'water fast quench' but without the steam bubble insulation issues. Occasionally a knifemaking supply house would buy a lot and break it down, but I haven't looked for that in a few years.

http://www.mcmaster.com/#quenching-oil/=mv0r7t
http://heatbath.com/heat-treating-products-2/oil-based-quenchants/

It is a really fun topic that I wish I had time to fully investigate...but I already have too many hobbies! I have pretty much settled on stainless steel blades ground form barstock, so I send mine out for heat treating by professionals using either vacuum furnaces or molten salt baths. A guy's gotta know his limits!

- - - Updated - - -

As for your surface hardening, why not through harden? Start with higher carbon steel and just fully harden it. Is it a toughness issue where the full hard and tempered material is just too brittle?

I always think if rifle receivers in cases like this. As soon as good alloys were available for through hardening, case hardening virtually disappeared from the rifle making industry in the early 1900's...with good reason. Case hardening adds an extra step that is just not needed in most cases.
 

Ray C

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cdhknives...

Much thanks for the thoughtful reply and product links.

The stuff I work on is either for my own shop-made equipment (in which 1045 is just fine) or for adaptors of various sizes to convert pulleys, sheaves etc. and a handful fabrication parts for lawn mowers and tractors that do not really even need the surface hardening. This is all a lead-up to the bigger picture/plan I have in mind.


Ray
 
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