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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #61  
Old 07-17-2004, 04:05 PM
JimmySeymour JimmySeymour is offline
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I've heard of people putting there quenching oil over brine so there is a zone of differential heat absorption to create different effects. I've never tried this or seen anyone do it. Is this another myth?

Not to stray to far off the topic but we had a Tiawanese student in my damascus and handles and guards class that came to the abs school because he couldn't get a real answer in his home country. He asked a local bladesmith how he got the colors in the steel from heat treating the knife. He was told that the sword in question got it's blue color because it was placed in a rainbow at a waterfall and allowed to absorb the color over 3 years. We had a pretty good laugh at that one.
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  #62  
Old 07-17-2004, 04:30 PM
fitzo fitzo is offline
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There is a crowd that hangs out in oft-moving places that is quite adept and knowledgeable in HT metallurgy and beyond to creating their own steel. At one time they hung out more at Sword Forums, then later at Fogg's forum. I don't know where they hang nowadays. Kevin knows, I'll bet; he's one of "THEM" ! I feel confident the Clark swords are the result of deep understanding of heat treat metallurgy.
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  #63  
Old 07-17-2004, 06:26 PM
Quenchcrack Quenchcrack is offline
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Colors in the steel

I am assuming you are all refering to what was once called "color case hardening". This is a process that was commonly used on Colt pistol frames. It is done by bubbling air through the oil quenchant. It must be precisely controlled to get a pleasing coloration. I believe an old edition of Machinery's Handbook describes the process.


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  #64  
Old 07-17-2004, 07:45 PM
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Chuck Burrows Chuck Burrows is offline
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Color Case Hardening How-To:
"To case harden a part (the process is also known as pack hardening) the finished low carbon steel part is placed in a sealed container, packed with a high carbon compound. In the old days this was simply animal hide or bone. The container filled with parts and carbon bearing material was brought to a red heat and held at that temperature for a time determined by the size of the part. The time might be from a half hour up to several hours. As the bone or hide became carbon in the container, and a carbon rich gas formed, some of the carbon would infuse into the surface of the steel. Over time this would penetrate several thousandths of an inch, producing a high carbon surface on the low carbon steel part. At the proper time the container is removed from the furnace and the contents dumped into a quenching bath, usually water with perhaps a surface coat of oil to lessen the shock of the quench. The high carbon surface skin becomes glass hard, but the low carbon body of the piece remains soft and very ductile and able to resist shock. Properly done it made a simple and very durable system for treating metal action parts.
Colors are produced when the steel surface is cooled unevenly, capturing the natural blues, oranges and yellows of cooling steel. Several methods are employed to do this. Stevens moved the parts into the quench in a jerky fashion, producing a barred effect of color. Perazzi did the same. In the London gun trade the quench bath, usually a barrel with soft water and a skim of oil, was agitated by stirring, or with bubbles of air, producing a mottled effect on the steel. "

"Color case hardening is done much the same way except that generally only leather and bone are used as the carbon source. I don't know why this works better than charcoal, but it does. You get more brilliant colors with them. The other thing you do is modify the quenching bath. You need a source of bubbles. LOTS of bubbles to really rile up the quench bath. Adding a bit of potassium nitrate to the water increases the brilliance of the colors as well, but isn't a requirement. You have to watch the temperature more closely with color case hardening or the colors won't come out well. Don't go over 1350 F. "
A restored Colt SAA with CH frame and charcoal blue barrel and grip frame by Turnbull Restorations


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Last edited by Chuck Burrows; 07-17-2004 at 08:17 PM.
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  #65  
Old 07-18-2004, 06:52 AM
Quenchcrack Quenchcrack is offline
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Color Case Hardening

Yeah, what Chuck said. Beautiful piece.

Now you have me wondering. If the source of the carbon is critical to the coloration, simply applying this method to a high carbon blade may not give the same results. Ok, so how do you get the rainbow on the edge? Are these actually temper colors?


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  #66  
Old 07-18-2004, 10:39 AM
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Chuck Burrows Chuck Burrows is offline
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Ok, so how do you get the rainbow on the edge? Are these actually temper colors?
Apparently yes - Tai Goo who has done the most experimentation with rainbow qenches has always agitated it when going into the quench and when you note that agitation is also critical to getting the colors when color case hardening then I believe that is what at least in part gives the colors when rainbow quenching or at least plays apart. One should also note that "good" hamons are dependent on the type of steel used (10xx steels give the most dramatic hamons) so that also probably has a bearing on the rainbow quench.

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Colors are produced when the steel surface is cooled unevenly, capturing the natural blues, oranges and yellows of cooling steel.
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Stevens moved the parts into the quench in a jerky fashion, producing a barred effect of color.
This one sounds real familiar because it was during Tai's first "in and out" quenching method that he started noticing the colors. Oxygen apparently may also play a aprt in the colors but they are not just surface oxides. I have one of Tai's rainbow quenched blades on hand and the colors are definitely "in" the steel and not just a surface condition.


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  #67  
Old 07-18-2004, 12:01 PM
Gary Hamilton Gary Hamilton is offline
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Chuck, the pistol looks nice. You mentioned that you have one of Tai's knives with the rainbow quench. I would enjoy seeing it if you have time to snap some photos. Everything he does seems to leave me in awe.


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  #68  
Old 07-18-2004, 12:23 PM
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Chuck Burrows Chuck Burrows is offline
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Howdy Gary-
Heres the link to Tai's post re: the knife I have on hand (it's not mine - I'm to make a display box for it)

OOPS! forgot the link - http://knifenetwork.com/forum/showth...highlight=hemp


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Last edited by Chuck Burrows; 07-19-2004 at 10:56 AM.
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  #69  
Old 07-19-2004, 08:35 AM
Kevin R. Cashen Kevin R. Cashen is offline
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Originally Posted by fitzo
There is a crowd that hangs out in oft-moving places that is quite adept and knowledgeable in HT metallurgy and beyond to creating their own steel. At one time they hung out more at Sword Forums, then later at Fogg's forum. I don't know where they hang nowadays. Kevin knows, I'll bet; he's one of "THEM" ! I feel confident the Clark swords are the result of deep understanding of heat treat metallurgy.
8o SHHHHH! The underground movement that you speak of is very guarded with their arcane secrets. I could tell you where the secret meeting place could be next for the League of Metallurgical Bladesmiths, but I would not live long enough to make it to that meeting In fact that is all hypothetical since I know nothing of any such group! I know nothing I tell you! I swear on my pocket protector and my type K thermocouplers! 8o
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  #70  
Old 07-19-2004, 10:14 AM
fitzo fitzo is offline
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hehe....
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  #71  
Old 07-19-2004, 05:40 PM
Gary Hamilton Gary Hamilton is offline
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Chuck, thanks for the pic. I missed this one during my time lurking.


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  #72  
Old 07-19-2004, 09:14 PM
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Guys, I believe we may have taken off on the wrong tangent with jummy's original question. Or at least, the first thing that popped into MY head was floating oil on water for a duplex quench bath to gain something of the effect of both an oil quench and a water or brine quench. Tthe idea is that as you pass the hot blade through the layer of oil it is cooled enought to allow it be safely quenched in the more severe quenchant in the second layer. You could also do an edge quench type hardening with brine for the edge layer, and heavy oil for the spine. If you did it just right, you might get a nice differential hardening. Anyway, this oil on water thing is common in the common mechanics shop manuals of 75 years ago.


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  #73  
Old 07-19-2004, 10:55 PM
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I don't know much about the heat treating, or even heat treatability of lead, but the family of a friend of mine is in the ammo making buisiness. And my buddy has talked about setting up his own little buisiness of making lead shot. For shotguns. This thread reminded me about him trying to explain there quench process of the molten lead. (note this was before i was into smithing of any kind.) They use the exact process being discussed here. A level of oil over the water. He mentioned it was for that exact reason. Cooling the lead to a degree where the water doesn't shock the lead.

I'm curious as to if anyone has done this yet, and how well it worked?

Also i have a small side question. How much would the weigh of the oil 5w30, 40w, etc have an affect on the quench? Would a heavier oil quench faster or slower? Or would they be the same? I've been using a quenchant of 50% ATF and 50% oil. Mixed oils though, a little of every weight probably. And I feel my quench has been to slow. I have about 10 gallons of quenchant, but even after a 30 second quench, it will still sizzle pretty heavy in water. just came to me that its possible i'm over heating the metal, but i'm still curious on what oil weight is most common.
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  #74  
Old 07-19-2004, 11:19 PM
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Quote:
Also i have a small side question. How much would the weigh of the oil 5w30, 40w, etc have an affect on the quench? Would a heavier oil quench faster or slower? Or would they be the same? I've been using a quenchant of 50% ATF and 50% oil. Mixed oils though, a little of every weight probably. And I feel my quench has been to slow. I have about 10 gallons of quenchant, but even after a 30 second quench, it will still sizzle pretty heavy in water. just came to me that its possible i'm over heating the metal, but i'm still curious on what oil weight is most common.
I've wondered exactly what difference oil weight makes too. I also use 50% ATF and 50% oil, both are not used and the oil is 5w20 semi-synthetic. I choose the oil on the assumption (hopefully it's right) that thinner oil quenches faster, and I took the semi-synthetic since I thought it might help raise the flash point.

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And I feel my quench has been to slow. I have about 10 gallons of quenchant, but even after a 30 second quench, it will still sizzle pretty heavy in water.
The boiling point of water is way lower then the 400ish F needed to quench to for hardening, so it'll still make the water sizzle even when quenched enough for good hardness. As long as the file skates, it's good.


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  #75  
Old 07-19-2004, 11:23 PM
ironbasher ironbasher is offline
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Question League of metalurgical bladesmiths

Kevin How about a league of metalsmiths forum where only an approved list of people get to post and answer? The rest of us could only look and learn! I used to look in on swordforum when you and Howard Clark and Papa Meier used to post, then it got invaded by a bunch of nincompoops who clearly werent working blade smiths as the intro requested. The magazines are sometimes no better, with pixie dust theories being advanced with a heavy dose of self promotion, it is hard to separate the wheat from the chaff, and find real world workable info beyond the basics. Ironbasher
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