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Tempering Hardened W1?

NoraE

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Jul 26, 2020
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Hello All

I've been trying without success to soften 2mm W1 that has been heated to 1500* F and quenched in water to a workable hardness. I've been using a toaster oven that has a high end of 485* F.
I've tried various times and temperatures but still it renders my HSS gravers useless in under 3 minute each.
For one example, I've heated it for two hours and is still to hard, then put back in for another two hours but don't notice much of a change. Did the second heat cycle not do anything to further soften it? Should it be rehardened first, then heated again for longer to see a change?
I have a copy of "Hardening, Tempering & Heat Treatment" by Tubal Cain. Yet still I'm confused.

Any help would be appreciated.
 

John MacArthur

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Feb 13, 2007
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Did it turn blue? I think 485F is not hot enough for W1, you'll need more like 575 to 600, and it'll still be pretty tough. It should turn dark blue. The second heat at the same temp won't change the hardness much, if at all. And depending in the size of the piece, you shouldn't need two hours, but just a minute, especially if it's small.
Johnny
 
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glenhead

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(Another TL/DR, sorry.) Yeah, 485F/252C is only tempering to a yellow-orange, which is a good temper for the blade in a woodworking plane. Danged hard, in other words. As you've seen, HSS will cut it, but it'll dull the graver quickly.

If you want to harden and temper the piece before you cut it, you'll need to heat it to about 575F/300C for the temper. That'll be a nice dark blue, which is about as hard as we need anything to be. It also works well to make the piece and then heat treat it, but you have to be concerned about warping long skinny pieces if your quenching technique isn't perfect.

For the stuff we deal with, once a piece of steel is hardened, the amount of time it spends at a temperature is pretty much irrelevant. It can spend the next hundred years at 300F/150C and it'll still be fully hard. (Well, except for the tiny bit of softening caused by the inter-atomic forces themselves, but that's another story and can be ignored for our purposes.) There are some exotic alloys that will do things if they spend a long time at lower temperatures, and there are a few techniques for cryogenic tempering, but that another-another story. Repeating it won't make any difference. You HAVE to get it to the specified temperature in order for it to temper as you want it to. Temperatures lower than that don't change the metal at all. That's why mainsprings don't "lose their temper" in an ultrasonic cleaner. Springs are usually tempered to a blue, and you have to get them above 575F/300C to change their characteristics. The white alloy mainsprings used in modern watches are even more stable than that.

For pieces the size we deal with, the piece is going to be within a very few degrees throughout its thickness. "Soak time" is the time needed to get much larger pieces to equalize throughout their matrix. An old saying is "an hour per inch of thickness", or about two and a half minutes per millimeter of thickness. Again, these numbers are used primarily for plate steel. 2mm round stock doesn't need to spend any real time soaking. There just isn't enough mass to make a difference. Soaking isn't going to hurt anything, it just wastes fuel or electricity for our purposes. Now if you're hardening and tempering a 1"/25mm cube for some sort of tool or something you'll want to soak it, but little stuff? Nah.

So what do you do? Go to the big-box "home improvement" store (or an old-fashioned hardware store) or anywhere that has a key-cutting machine. Ask someone at the store to give you the brass shavings from the machine. I was able to get three coffee cans full of shavings in a half-dozen stops. A small cast-iron skillet is the perfect holder for this technique. Put a layer (1/2"/13mm thick or so) of brass shavings in the skillet. Nestle the hardened part in the top of the shavings, but make sure you can still see it. Lay it on top (put it to bed) and nestle it in, don't poke it in vertically. The shavings will spread the heat nicely across the whole part. Make sure you have bright light on this setup - you need to be able to see the part well. It's best if your part is polished well; it'll make it easier to see the color change. Put the skillet on the stove and crank up the heat. Keep an eagle eye on the part and watch for it to start changing colors. It'll first start showing a faint yellowish cast, and that will darken through to brown and pinkish purple and then through purple to dark blue. The color changes can progress quickly, so pay attention. Once it hits dark blue it's tempered. You can grab it from the shavings (using pliers or tweezers or something, it's still DANGER hot) and quench it or run it under tap water or whatever to cool it down so it doesn't over-temper. It also works really well to just dump the whole skillet-full of part and shavings into a container of water. It can't re-harden without being heated to well over twice the blue temperature, so quenching from these temperatures is just to cool it down.

You can also put another polished piece of steel (like a screw or something) next to the part to use as a color reference. Any steel will do to show the colors. It doesn't matter what kind of steel the reference piece is or whether it's hardened or not. I have a piece of 12L14 rod (non-hardenable) that I polish up to use sometimes.

For itty bitty pieces I have an old serving spoon and an old tin egg separator that I use for the shavings. I made and treated a pocket-watch winding stem yesterday. I clipped the egg separator in the two clips of a "third hand", filled the little cup with shavings, laid the stem on top of the shavings and scrunched it down a bit, turned my LED desk light on it, and heated the bottom of the cup with a butane torch. (I regularly use an alcohol lamp on the egg separator, too, but it takes a lot longer than the torch, and it's out of alcohol right now.) Total tempering time was less than three minutes. Once it hit a deep blue I snagged the stem with hemostats and dunked it in my drinking water. (Don't tell my wife.)

This is one of those things that's a real joy to do once you learn how. There's unfortunately a lot of mystery associated with it because everything is written for things that are hundreds of times the size of the things we deal with.

I hope this helps.

Glen
 

DeweyC

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Feb 5, 2007
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Hello All

I've been trying without success to soften 2mm W1 that has been heated to 1500* F and quenched in water to a workable hardness. I've been using a toaster oven that has a high end of 485* F.
I've tried various times and temperatures but still it renders my HSS gravers useless in under 3 minute each.
For one example, I've heated it for two hours and is still to hard, then put back in for another two hours but don't notice much of a change. Did the second heat cycle not do anything to further soften it? Should it be rehardened first, then heated again for longer to see a change?
I have a copy of "Hardening, Tempering & Heat Treatment" by Tubal Cain. Yet still I'm confused.

Any help would be appreciated.
Buy a lab quality adjustable heat plate (Thermodyne, Corning, etc) off ebay. I marked mine to where it provides a nice deep blue just past purple. I use a pyrex bowl as a cover. I use this for heating alcohol for removing shellac and a host of other tasks. You can use an oven thermometer with it if desired, under the cover. Unlike the alcohol lamp and brass swarf technique, once it is set to blue of your choice, you can walk away for the day and it will still be the color you chose.
 

glenhead

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Buy a lab quality adjustable heat plate (Thermodyne, Corning, etc) off ebay. I marked mine to where it provides a nice deep blue just past purple. I use a pyrex bowl as a cover. I use this for heating alcohol for removing shellac and a host of other tasks. You can use an oven thermometer with it if desired, under the cover. Unlike the alcohol lamp and brass swarf technique, once it is set to blue of your choice, you can walk away for the day and it will still be the color you chose.
Yup yup, Dewey, a lab heating plate is a great answer. I have one of the danged things and haven't taken the time to set it up yet. I bought it to get the repeatability. (So if it's such a great answer, why is it still in its box? Hmm? Sigh.) Let's see, what pile of stuff is it in...

Glen
 

NoraE

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Jul 26, 2020
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It turned this color.

I called the local hardware stores that cut keys. Sadly none of them save the chips, nor are they willing. Of the current available choices are any of these offerings of suitable size? brass chips | eBay

I like the idea of the lab grade hot plate for repeatability. The descriptions aren't that great so a little research will be in order before a model is decided upon.

20210125_120706.jpg
 

glenhead

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Any of the first several eBay listings are just what you want. A pound of them will go a long, long ways, especially since you can just dump them back in the coffee can when they've cooled.

I didn't ask anyplace to save the shavings. I walked in with a coffee can (or a rinsed-out empty Slurpee cup I found in a waste basket once when I forgot the can) and found someone who knew how to operate the machine. In one big-box the guy who ran the department was a fanatic for cleaning the machine, so there was less than a teaspoon full. At the others there was a very gratifying pile of shavings.

If that's a picture of the rod after it came out of the toaster oven, it shows why you need to have a highly polished surface to see the color change. You can remove some of the black with sandpaper and give it a polish, then try again. At 485F the color change may be almost imperceptible - the yellows are hard to see if you're not familiar with them.

There's a good and simple experiment to show yourself the color changes. As I said before, carbon steel will progress through the colors regardless of its hardness or temper. (Some stainless will, too, but W1 is a for-sure.) Take a rod and polish the surface. It doesn't have to be perfectly shiny-smooth, but the shinier the better. For a quick polish on a rod like that I chuck it in a cordless drill and use 360-grit sandpaper to polish it - quick and simple. Once it's polished, hold it by one end and put your torch's flame half way down the rod. (This is also a great way to experiment with the heating capability of the various parts of the flame. The fringes of the flame are far gentler than the blue cone in the center.) Watch how the colors progress as the rod heats up. Near the flame the colors will change more quickly as they shift past blue to gray. As you get farther away down the rod from the heat the colors will progress from gray to blue to brown to orange to straw to yellow and back to silver. If you stop heating before the far end of the rod changes colors and quench the rod you can see the whole color progression. If you overshoot and the whole thing turns blue, just polish it and try again. That's a great experiment to learn the colors. As long as you don't heat the steel hot enough to glow you won't affect the crystalline structure of the steel.

That experiment also proves that you can use a live flame to temper. It takes a whale of a lot more attention with a small piece, but it really does work nicely. With a long piece over an alcohol lamp flame you can really see what's happening. As the colors start to change you can chase the color along the length until you coax the whole thing into a very pretty blue. I find it kind of zen.

Enjoy the journey of learning.

Glen
 
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Betzel

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I'm always amazed what I learn just lurking, so thanks.

I have not tried it, but heard from an mid timer that old timers used to blue small and thin material (like hands and springs) with hot bars through surface contact. Apparently, this can also work as a "touch up" for visual effect, like after rust removal becomes too aggressive. I would think you would have to been pretty keen to rub a hot steel bar across (or near?) thin material to blue it evenly, and even keener to do spots. Has anyone else heard of this or tried it?
 

gmorse

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Hi Betzel,

I would think you would have to been pretty keen to rub a hot steel bar across (or near?) thin material to blue it evenly, and even keener to do spots. Has anyone else heard of this or tried it?
Some of the old Clerkenwell hand makers had a small copper anvil mounted over their open coal-fired ranges and used that for 'touching up' their hands. The main bluing was sometimes done over a Bunsen burner, which needs a great deal of skill!

Regards,

Graham
 

NoraE

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Jul 26, 2020
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Polished with #400 and tossed bask in the to the toaster for color verification.

20210127_114804.jpg
 

glenhead

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Am I hallucinating again or is that a deep blue? If it is, then your toaster oven gets a heckuva lot hotter than it says it does. As I said earlier, a deep blue is sort of a "default" color for a whole flock of applications. It gives a nice balance of hardness and toughness and workability.

In general, steel dulls HSS cutting tools a lot more quickly than anyone wants it to. If you need to heat treat the steel before you turn it (so that you don't have to worry about warping or whatever) then your tools are going to lose their edge faster than if you turn it fully annealed. HSS bits with cobalt (M35 has 5% Co, M42 has 8%) are harder than regular high-speed steel, so you may want to invest in a few of those. Cobalt bits hold their edge a bit longer.

Glen
 
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NoraE

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If it is, then your toaster oven gets a heckuva lot hotter than it says it does.
My shop toaster oven is about 20 years old and has a knob that points toward what ever printed number on the scale you choose, 500* F is the highest, nothing digital on this thing. The temp is measured with an infrared thermometer.
I'll have to throw something harder for gravers ito the cart after the 1st and give them a try.
 
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NoraE

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Jul 26, 2020
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Buy a lab quality adjustable heat plate (Thermodyne, Corning, etc) off ebay.
I found a Corning PC-35 for cheap. That model is listed to 510*C / 950*F, hopefully that will be hot enough to transfer the heat threw a tuna can full of the brass chips that was ordered earlier.
 

Jerry Kieffer

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May 31, 2005
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Hello All

I've been trying without success to soften 2mm W1 that has been heated to 1500* F and quenched in water to a workable hardness. I've been using a toaster oven that has a high end of 485* F.
I've tried various times and temperatures but still it renders my HSS gravers useless in under 3 minute each.
For one example, I've heated it for two hours and is still to hard, then put back in for another two hours but don't notice much of a change. Did the second heat cycle not do anything to further soften it? Should it be rehardened first, then heated again for longer to see a change?
I have a copy of "Hardening, Tempering & Heat Treatment" by Tubal Cain. Yet still I'm confused.

Any help would be appreciated.
Nora
I do not recall if we have had this discussion before or not. If so, disregard.

Metals are not created equal even if the alloy designation is the same.

The color of hardened/tempered metal is only a rough idea of hardness and is not near accurate enough to determine or create free machining status.
There are many procedures that can be utilized to produce decorative color shades in metals such as those utilized in screw heads, hands etc.

However, if metal is being tempered for the purposes of machining, then you are entering the world of Rockwell hardness or Rc.
The first attached photo is of a sample chart that lists the Rc of various carbon alloys at the same blue steel color per red arrows.
At a Rc of 47 your HSS cutting tools should do the job, but at 58 or 59 it will likely tear them up in short order. As you can see, the same color can produce a very wide range of hardness.

To be successful, you first need to know the maximum Rc hardness your cutting tools are rated for that can be supplied by the tool manufacturer.

Next you need to know what Rc that is required for the job and then the exact temperature to achieve it, again supplied by the manufacturer of the steel stock.

In the machine tool business, setup time and tool life often determines success or not. As such, they depend on their metal suppliers and tool suppliers to supply materials and tooling that work together.
By purchasing from those same reputable metal suppliers that service industry, you can greatly benefit from the same consultation.

Not knowing anything about your cutting tools, assuming no factory support, I would suggest starting out at a Rc of about 48 and work your way up slowly to determine the capability of your tools. While there will always be exceptions, most horological items will not exceed a Rc of about 55

If you do not have a accurate method of controlling tempering temperature, you may want to consider the following product to assist.


Jerry Kieffer

fullsizeoutput_7d8.jpeg
 
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DeweyC

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I found a Corning PC-35 for cheap. That model is listed to 510*C / 950*F, hopefully that will be hot enough to transfer the heat threw a tuna can full of the brass chips that was ordered earlier.
Yep, I have one of those. The enamel top is easier to keep clean than the Thermodyne. I do not bother with the brass chips. Just lay the work on the surface and cover with pyrex.
 

NoraE

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Jul 26, 2020
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I do not recall if we have had this discussion before or not. If so, disregard.
We have, in the "I'd like to learn" stage of heat treating. However I still like to hear the long answer again. You have added new information for tempering and a chart. TY. I save all of the posts that I find helpful to a file for future reference. The efforts of those who help me are not waisted.

I've got an infrared thermometer that works well for temps bellow 1022*F. However I did buy the 1500*F Tempilaq on your suggestion for heating.
 
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