"hardened" freeze plugs

[desertland]

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[Tony M.]

You more or less have the method down, however, I think you might be overlooking case hardening unnecessarily.

Look into the product "Kasenit" and do a little research on the removal of the zinc plating. The end result will be a baffle with a hard surface to resist erosion, but enough elasticity to prevent cracking.

Using a surface hardening compound like Kasenit will be nearly as easy as using the superquench method, and will provide more consistent results.

[M1-Dan]

Desertland the way I did my freeze plugs I had also searched around on this forum at other builds. I had read sub-sonics build and saw that was his way of treating the plugs so I went that route. Not sure if it accomplished a lot but did seem to at least surface harden them. Only time will tell and hope that won't be for a long time. In the future for another build I will plan on using all stainless and hopefully at that point have a lathe to make some solid baffles. But in the mean time freeze plugs seem to work quite well and so far very impressed.

[desertland]

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[desertland]

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[M1-Dan]

I didn't feel picked on at all, I'm glad this topic started as a way to get more info on the subject.

[Hard_ware]

Take the freeze plugs before you heat treat them, and drop them on a hard surface and listen to the tone produced.
Now heat treat them, I heated with mapp gas until glowing cherry red and dropped into salt/ice/soap solution, then heated with propane flame until slightly blue haze around them and let cool off to ambient temp.

Then drop them and see the sound difference they make. Completely different sound. Something happened to the molecules what exactly I don't have a scanning electron microscope so I can't say for sure, but resonance has changed drastically.

Go buy a tempered bicycle part or hardened steel part something with similar thickness to the freeze plug and drop it and notice the sound it makes.

Remember how the hardened freeze plug sounds, wow just like the purchased hardened part.

I was told about the sound from a old man from vietnam that would repair bikes. He would buy bike parts and only the the ones that had a ring to them, he said they would never go bad. The parts that didn't ring would wear out soon.

Not sure if it makes any difference but my freeze plug suppressor still going strong.

Subsonic Thanks!

and all the rest who have posted as well, sharing info you keep what works and toss what does not, after all it didn't cost anything.

[desertland]

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[Hard_ware]

To help prevent them from being too brittle and crack.

[Tony M.]

Have you worked with cherry red or kasenit yourself?

Yes, but rarely, it's the kind of thing that can make a difference for certain applications, but I had multiple forges, kilns and heat treat ovens, so I generally went other routes.

Adding carbon to the base metal is a great way to get a real case hardening, but realistically beyond the capabilities of most folks. If you're interested in recipes for real 'color' case hardening mixtures, I've done plenty of that too, but kind of beyond the needs and reach of most home builders.

If the freeze plugs you're using will harden to satisfaction, then by all means, go that route. Be sure to temper them, even if they don't get super hard, it helps prevent stress fracturing. If you find they aren't as hard as you'd like, then you can always use the Kasenit afterwards.

One thing I would recommend; chemically remove the zinc from the plugs, no matter what direction you go. It's pretty bad for you when inhaled.

[Hard_ware]

Have you worked with cherry red or kasenit yourself?

Yes, but rarely, it's the kind of thing that can make a difference for certain applications, but I had multiple forges, kilns and heat treat ovens, so I generally went other routes.

Adding carbon to the base metal is a great way to get a real case hardening, but realistically beyond the capabilities of most folks. If you're interested in recipes for real 'color' case hardening mixtures, I've done plenty of that too, but kind of beyond the needs and reach of most home builders.

If the freeze plugs you're using will harden to satisfaction, then by all means, go that route. Be sure to temper them, even if they don't get super hard, it helps prevent stress fracturing. If you find they aren't as hard as you'd like, then you can always use the Kasenit afterwards.

One thing I would recommend; chemically remove the zinc from the plugs, no matter what direction you go. It's pretty bad for you when inhaled.

+1 on that !

But if burning it off make sure your outside and up wind from the vapors & smoke, it's very bad stuff !!!

[desertland]

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[Elkins45]

That was why I dismissed REAL case hardening. The time and equipment investment to do a few dozen plugs would make just buying an off the shelf can affordable. It's another story if you already have black smithing equipment.

A hibachi, hardwood charcoal (sold as 'cowboy charcoal' at places like Lowe's or HD) and a leaf blower are a passable substitute for a lot of real black smithing equipment. Toss them in used motor oil to quench, repeat a few times, then finish up with the super quench treatment. Might as well run a few cycles in the oil, since you have already blazed up the charcoal.

I haven't done this with mild steel freeze plugs but I certainly can vouch that this setup will take 1095 stock past the Curie point to make a hardened knife blade.

[desertland]

A hibachi, hardwood charcoal (sold as 'cowboy charcoal' at places like Lowe's or HD) and a leaf blower are a passable substitute for a lot of real black smithing equipment. Toss them in used motor oil to quench, repeat a few times, then finish up with the super quench treatment. Might as well run a few cycles in the oil, since you have already blazed up the charcoal.

I haven't done this with mild steel freeze plugs but I certainly can vouch that this setup will take 1095 stock past the Curie point to make a hardened knife blade.

That is what I've found as well, turning a known mild steel alloy like 1095 into a hardened edge. Talk has been on 3/16" to 1/4" thick stock.

What would be interesting to know / learn is if it is worth the effort?

Lets just say a freeze plug can with cold pressed untreated plugs had a life span of 5000 rounds. Based on typical plinking and doing tactical style shoots. No leaning on the full auto for half a dozen 30 round mags.

So if a full scale case hardening was done and you gained an additional 1000 rounds of life span it could be questionable as to the effort being worth the gain.
Say the super quench maybe did little more than a gain of another possible 500 rounds. For a simple process that takes little in tools or time I could see it worth doing. Or just saying to hell with it.

On the flip side, lets say untreated freeze plugs may hold up for 2000 rounds. Same shooting style as above.
Say doing super quench gained another possible 1000 rounds of life. Full on case hardened brings it up to a total possible life of 5000 rounds. That would make going through the effort a different story.

Searches on freeze plug cans bring up lots of "this is how I did it" kind of information. I've yet to find any quantifiable info on the base life vs treated life of freeze plugs in the baffle application.

I tried looking up hot gas erosion on metals and found this: http://cdn.intechopen.com/pdfs-wm/44450.pdf Short version, look at the pictures on page 8 and then data on page 12.

[Tony M.]

That is what I've found as well, turning a known mild steel alloy like 1095 into a hardened edge. Talk has been on 3/16" to 1/4" thick stock.

Just to clarify, 1095 is hypereutectic steel (high carbon, with enough carbon that it doesn't dissolve all of the carbon into solution during normalization) and actually very easy to harden, and will require tempering to prevent stress fractures) It's a 'simple' carbon steel, but certainly not a 'mild' steel.

The most common mild steels are 1018 and A36.

1018 has a specific chemistry, (10 denotes simple carbon alloy, 18 denotes 0.18 percent carbon) whereas A36 is defined by minimum yield strength and not chemistry, and as a result varies widely in specific alloy composition and carbon content.

Freeze plugs are likely to be made out of something like A36 or something similar that may or may not harden acceptably. If they don't. then the Kasenit or similar can provide some improved strength.

As for the question of the benefits of hardening, as a rule, increasing the hardness will increase the wear life of the surface significantly.

The thing we haven't talked about is the heat. Since most simple steels are tempered at between 350 and 500 degrees Fahrenheit. If the baffles will reach temperatures (not just be exposed to them) that will be above whatever the temper is, then the heat treating will have reduced effectiveness.

There are plenty of exotics that have less issues with these things, but since they don't generally make freeze plugs out of exotics, I won't bother talking about them.

[desertland]

The thing we haven't talked about is the heat. Since most simple steels are tempered at between 350 and 500 degrees Fahrenheit. If the baffles will reach temperatures (not just be exposed to them) that will be above whatever the temper is, then the heat treating will have reduced effectiveness.

OK, this is a good point to clarify. Just for argument sake lets say the freeze plug has enough carbon in it that you do in fact make a gain in hardness. Via what ever heat and quench method, lets say you gained all your going to get. So far of all the freeze plug hardening stories I remember reading, they speak of another low temp heat and slow cool to take the brittleness out.

Not knowing any better it sounds a bit contradictory. Lets go to this effort to harden it only to make it just a but softer? If you just hardened them and installed them in the can they would ( could ? ) anneal just from use?

[Tony M.]

OK, this is a good point to clarify. Just for argument sake lets say the freeze plug has enough carbon in it that you do in fact make a gain in hardness. Via what ever heat and quench method, lets say you gained all your going to get. So far of all the freeze plug hardening stories I remember reading, they speak of another low temp heat and slow cool to take the brittleness out.

Not knowing any better it sounds a bit contradictory. Lets go to this effort to harden it only to make it just a but softer? If you just hardened them and installed them in the can they would ( could ? ) anneal just from use?

What we're looking for is a temper cycle, not an anneal cycle.

The issue with 'temper in use' would be that the baffles will be subjected to pressure spikes before they would ever come to temperature. If you managed to get them very hard, they would likely break apart almost immediately, that wouldn't end well.

It's unlikely that you'd get the freeze plugs hard enough for them to shatter, but taking a temper cycle will prevent the possibility.

Skipping the temper cycle would be super lazy, and frankly, just a bad idea. Hell, once the baffles are hardened, you can throw them on a cookie sheet in the oven for an hour at 400, and call it good.

If the baffles don't get that hard, the temper cycle wont remove any hardness, if they did get very hard, it'll keep them from being brittle and prone to cracking and breaking.

[akraven]

You can try a simple test. Take a few freeze plugs and run a file across them and see how it "bites" into them,easy,hard,medium?? Now try your hardening method of choice. Before tempering them try the file again. If they are truly able to be hardened they should now be hard and the file should bite less or not at all. While wearing all needed safety equipment in case they truly are brittle and shatter into shards hit one with a hammer and see if it fractures,shatters or just bends and compare that to an untreated one.

Safety warning in case you missed/ignored it above if they truly can be fully hardened then they can actually shatter into many sharp fragments and could cause your body some damage so Eye pro,Hand pro etc is a important thing.

[desertland]

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[Fulmen]

Skipping the temper cycle would be super lazy, and frankly, just a bad idea. Hell, once the baffles are hardened, you can throw them on a cookie sheet in the oven for an hour at 400, and call it good. If the baffles don't get that hard, the temper cycle wont remove any hardness, if they did get very hard, it'll keep them from being brittle and prone to cracking and breaking.

I concur. Chances are the baffles will subjected to this level of heat anyways, so there isn't anything to loose from a temper. And there is much to gain as they can be brittle enough to fracture from impact.

[rodpiper]

Drop the red-hot item into seltzer water and voila, the item will suck in carbon.

[Capt. Link.]

Drop the red-hot item into seltzer water and voila, the item will suck in carbon.

Never read this in metallurgy classes.
The introduction of carbon by the base metal is not mentioned in this patent.

US 5681407 A

(a) providing a liquid reservoir of coolant which is open to ambient pressure, said liquid having a temperature from about 100° F. to about 180° F. and consisting essentially of water and sufficient quantity of deliberately dissolved carbon dioxide to retard cooling as compared to water of the same temperature without said deliberately dissolved carbon dioxide, the amount of said dissolved carbon dioxide being present from about 0.01 to about 0.10 standard cubic feet of gas per gallon of water, the dissolved carbon dioxide being higher for lower water temperatures and lower for higher water temperatures; and

A freeze plug is low carbon steel.The introduction of carbon to form a case is done at high heat in the absence of oxygen or nearly so to help prevent scaling.Carbon rich gases like cyanide introduced in atmospheric ovens will impart the higher concentration of carbon necessary for case hardening.This process and others will never reach the level of hardness for the plug to become brittle and shatter.Once the case layer is penetrated you will have rapid erosion.You will still at all times have corrosion to contend with in the very hostel corrosive environment.Short of sending the plugs to a FFL licensed metal treatment facility the suggestion of Tony M. & Kasenit is the simplest to effectively carry out.

[Hard_ware]

Here is a link to some simple hardening methods

http://www.gun-tests.com/special_report ... BNI1JTHJ4I

[rodpiper]

You can also sandwich red hot item (the hotter the better) between two pieces of dry ice. Don't take my word for it, try it. Fast cool and you get migration of C into the metal.

[Tony M.]

You can also sandwich red hot item (the hotter the better) between two pieces of dry ice. Don't take my word for it, try it. Fast cool and you get migration of C into the metal.

No.

Rapid cool allows what carbon is in the steel to harden it. It does NOT impart carbon.