Any Metallurgists? Quench Advice For Steel

CCI

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Jul 15, 2009
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New Mexico USA
A bowl gouge for turning wood made from a piston wristpin. Want to harden the edge slightly, thinking maybe there is some way to determine if oil, water, or brine might be the better quench.

Any experience in such things?
 
I have experience heat treating steels and superalloys.

How large is the whole pin roughly? What do you plan on using the ends of the pins for. Meaning, how will you use the pin, secure it, attach it to something to hold the part. Just curious about the desired hardness across the profile of the pin.
Place the pin in a vise for stability when heating it, put the cold side of the treatment in the vise, and the portion to be hardened upward of course. For most steel hardening heat treatments, oil was used as a quenchant. I would get a "cup" type of object, and fill it with a petroleum based oil. Used oil will work fine for the application. Using most appropriately a propane torch, heat the edge or end to be hardened until it glows a dark orange / red color. This will hopefully get up to around 750*C (I only used celsius, my F temps are mostly unknown) hold the color for a min or so, being very careful to not overheat the edges, and burn it. Thinner the edge, easier to burn / overheat. After the color was good for about a minute, carefully remove the cold side of the rod from the vise while keeping heat on the hot side, and plunge it into your oil, gently moving the part around the oil. Let it cool for a bit before you touch it, it takes a time to cool.
The thing I've seen on that "forging fire" show to check for hardness, is to drag a file across the hardened area. If it skates nicely across the area, you're probably at a hardness that can be sharpened to a nice edge. I only used mechanical hardness testers at work, I have no idea of what the drag test is, or whatever that show does. As mentioned, we used a mechanical hardness tester to verify some of the results of our heat treats. Verifications were mostly done when the parts being treated needed a specific hardness value for a materials end use application or a hardness value that would make it possible for the shop to be able to machine a material in a much easier format being hardened. An example of machineability quality based on hardness values, would be when a soft metal is being machined, and it gums up all the tooling because it kind of smears into the tooling, making the part have a terrible surface finish quality and an inaccurate tolerance because of variations of the surface resolution. A common solution to soft metal machineability problems are to harden the material before it is machined. In general and to a certain point, a hardened material will be easier for tooling to remove material, have a higher surface finish quality, and in general a greater adherence to to part tolerances.

I've performed heat treats on small circular coupons of steel that were decreasing in value each treatment, and were all air cooled, also called an air quench. The point of the treatments was to make the highest hardness valued coupons, that were going to be used as a material for a freight train, diesel generator fuel injector nozzle. Super high pressures, needed a really hard and strong material and design that wasn't failing as early as the original ones were.
 
I have wondered about doing this for mower blade edges for durability.

Not the whole blade, as you don't want a hard blade that fractures on impact with something. But just the sharpening edge.
 
I have wondered about doing this for mower blade edges for durability.

Not the whole blade, as you don't want a hard blade that fractures on impact with something. But just the sharpening edge.
I've been trying to make the edges more durable too. A harder edge, will crack more in these applications. I did hear a super smart guy at work basically solve this issue, using a neat tool.
So instead of heating the steel of the blade, the machine deposits on the surface of the blade, a layer of tungsten wherever you aim it, its a concentrated point of application. You coat both sides of the entire blade edge, and you will have a surface that is extremely hard, insanely wear resistant, and the blade would retain its sharpness until you whacked a rock or something that would put a huge chip in the blade edge.
Last season I sharpened my blade edges on my John Deere about every 4 mows. I did randomly check the edge by just lifting the tractor up, and testing with my finger... My Brand new at the begining of the season blades were slightly rounded by the third use. Blamed it on sticks in the spring, and still sharpened them. Continued through entire season checking the edge condition each pre-sharpen of the blades. All the blades had rounded dents in them routinely after 3 to 4 uses, only one rock chip in one of the edges, it was not able to be sharpened at the chip, too much material was gone.
SO my observation is that the tip of the edge would wear down on the grass, sand, basically it was enough to round them off, very uniformly, over the entire edged surface on the blade.
The machine is expensive.
It takes lots of technique to work
It takes a lot of smarts to use it effectively
It would work best with brand new blades. The paint on at least the edges of the blades would have to be completely removed, and the metal surface would have to have any oils or other types of contaminates would need to be removed. Then, you get someone with skill and the tungsten material, and you coat the edges up. Hopefully you keep and angled edge, don't get the halfmoon shaped dents in the edge, and maintain a nice edge needing zero sharpenings throughout the season.

I am forgetting a drawback of this process, there is a clear reason why we didn't do it before.. I can't remember the issue, but it may have been something with the maximum thickness of each layer you can apply? IDK but the idea was hot in our group, and the guy was supposed to dig up / find the old machine in his garage, he is a real hoarder. All I know is that a tungsten coating on blade edges on paper would be very wear resistant. Much more resistant that the steel they use in the blades.
I'm sure part of the simple tech reason for the blades, is that they're well, just blades on a mower. Lots of people go years without even checking the condition of their blades. Tons of people just don't even care if the grass has a good cut pattern on the edges. Lots of simple just lets do it, don't care users out there. I bet the cost/sales values are iffy. I only know of three people that are smart enough and care enough to do it, I guess there is not enough demand for the product to create the solution.
 
I have experience heat treating steels and superalloys.

How large is the whole pin roughly? What do you plan on using the ends of the pins for. Meaning, how will you use the pin, secure it, attach it to something to hold the part. Just curious about the desired hardness across the profile of the pin.
Place the pin in a vise for stability when heating it, put the cold side of the treatment in the vise, and the portion to be hardened upward of course. For most steel hardening heat treatments, oil was used as a quenchant. I would get a "cup" type of object, and fill it with a petroleum based oil. Used oil will work fine for the application. Using most appropriately a propane torch, heat the edge or end to be hardened until it glows a dark orange / red color. This will hopefully get up to around 750*C (I only used celsius, my F temps are mostly unknown) hold the color for a min or so, being very careful to not overheat the edges, and burn it. Thinner the edge, easier to burn / overheat. After the color was good for about a minute, carefully remove the cold side of the rod from the vise while keeping heat on the hot side, and plunge it into your oil, gently moving the part around the oil. Let it cool for a bit before you touch it, it takes a time to cool.
The thing I've seen on that "forging fire" show to check for hardness, is to drag a file across the hardened area. If it skates nicely across the area, you're probably at a hardness that can be sharpened to a nice edge. I only used mechanical hardness testers at work, I have no idea of what the drag test is, or whatever that show does. As mentioned, we used a mechanical hardness tester to verify some of the results of our heat treats. Verifications were mostly done when the parts being treated needed a specific hardness value for a materials end use application or a hardness value that would make it possible for the shop to be able to machine a material in a much easier format being hardened. An example of machineability quality based on hardness values, would be when a soft metal is being machined, and it gums up all the tooling because it kind of smears into the tooling, making the part have a terrible surface finish quality and an inaccurate tolerance because of variations of the surface resolution. A common solution to soft metal machineability problems are to harden the material before it is machined. In general and to a certain point, a hardened material will be easier for tooling to remove material, have a higher surface finish quality, and in general a greater adherence to to part tolerances.

I've performed heat treats on small circular coupons of steel that were decreasing in value each treatment, and were all air cooled, also called an air quench. The point of the treatments was to make the highest hardness valued coupons, that were going to be used as a material for a freight train, diesel generator fuel injector nozzle. Super high pressures, needed a really hard and strong material and design that wasn't failing as early as the original ones were.
Original wristpin diameter is 0.792", it has been ground on one end to get a U profile so it can work as a gouge, the other end that is still round has a mild steel slug welded into it and that slug is welded to a piece of 3/4" black pipe for a handle.

If I take the steel to be hardened up until it becomes non-magnetic is this about right?

The edge is the only part I want to harden, the load on the tool is considerable, I don't want the whole thing to be brittle. I might even polish it out after the quench and heat it gently to bring it back down a little if a file doesn't scratch it slightly.

Thanks all for the replies.
 
Original wristpin diameter is 0.792", it has been ground on one end to get a U profile so it can work as a gouge, the other end that is still round has a mild steel slug welded into it and that slug is welded to a piece of 3/4" black pipe for a handle.

If I take the steel to be hardened up until it becomes non-magnetic is this about right?

The edge is the only part I want to harden, the load on the tool is considerable, I don't want the whole thing to be brittle. I might even polish it out after the quench and heat it gently to bring it back down a little if a file doesn't scratch it slightly.

Thanks all for the replies.
Yeah so that's a very small part, and the area to be hardened is smaller also. Heating steel to its non magnetic property as a guess of temperature is difficult based on the size, shape, and area of part to be hardened. testing the edge of the steel only for magnetism is going to be impossible because of the shape of the tip of the edge. Your magnetism test would detect magnetic steel from below the heated edge only. It wouldn't work as a way to test approximate temperature. The easier and better option would be, again, using the color to get an approximate temperature of the area heated. For hardening, you want a color of, again, say an orange with red color starting to become darker. Heat edge to temp for about two mins, dunk in oil and agitate, and hopefully you have a hardness value that will produce a very hard, sharpenable surface finish that will keep its edge for a long time!
 
You don't want to harden lawnmower blades. Hard = brittle. You don't want pieces of the blade going flying the next time you hit something you shouldn't.
 
Yeah so that's a very small part, and the area to be hardened is smaller also. Heating steel to its non magnetic property as a guess of temperature is difficult based on the size, shape, and area of part to be hardened. testing the edge of the steel only for magnetism is going to be impossible because of the shape of the tip of the edge. Your magnetism test would detect magnetic steel from below the heated edge only. It wouldn't work as a way to test approximate temperature. The easier and better option would be, again, using the color to get an approximate temperature of the area heated. For hardening, you want a color of, again, say an orange with red color starting to become darker. Heat edge to temp for about two mins, dunk in oil and agitate, and hopefully you have a hardness value that will produce a very hard, sharpenable surface finish that will keep its edge for a long time!
OK will do. And will report back here on the results.
 
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