Dusting off the cobwebs

[Ld Thomas Willoughby]

Just lay the barrel on its side and build a small clay dam around the patch, fill it with water and see if it leaks.

[Mac]

That seems like a fine idea! I think I have some Plasticine clay.

Thanks!
Mac

[Cet]

Mac, if the tank is a continuing problem I can loan you mine.

[Mac]

Thanks, Dave! I think I am going to have more trouble with the quenchant than the tank. My "glug" has been in storage for years and there is not really enough of it to fill the tank. I will give you a call later today, and see if you want to collaborate on some fresh brew.

Mac

[Mac]

Two out of three of my patches passed the test, and the place that failed was pretty dubious looking. It looks like a place that "boiled" while I was running a weld on the inside. I have re-welded that place from the outside, and unless there are rust-throughs that I don't see, the barrel is ready to use.

Now I need to look at the quench liquid that is stored in the 5 gal. buckets. I have been dreading this for a couple of years now.

Mac

[Mac]

This is much better than I had been fearing.

Only two of the bucket lids are cracked....



....and even in those, the solution looks OK. I expected to find mold, or huge gelatinous mats of bacteria, but I find nothing of the sort.


The glug in some of the buckets are darker than in others, but they were probably the ones nearer the bottom of the tank when I bailed it out five years ago. The darkness will be black oxide of iron.



The best part is that I appear to have nearly 10 gallons of what is probably undiluted stock in two of those white buckets in the foreground. The third white bucket has about 5 gallons of 15% solution. One of the orange buckets has the enigmatic note "13%" followed by a date from 06. It is about full. Of the other six, five are full and one is about half. My recollection is that I am using it at 13%, but I need to find the relevant notebook and decipher my notes.



Barring any of the sort of trouble where the stuff might have gone bad in spite of looking OK, it seems like I will be good vis a vis quenchant for this project.

Mac

[Jeremy.G]

Great!
Wish I could be there to witness some of the process.
I've quenched plenty of hot steel, but nothing near the size of a breastplate.

That's gotta be intense!

[Tom B.]

Mac,

Could you tell us a bit about the quench media you use and how you came to use it?
It seems most of the time I only hear people talk of using water, various oils, or a brine solution.

[Mac]

I am using an aqueous polymer quenchant by Houghton International. I found out about this class of medium while pouring over the heat treating literature back in 2001 or thereabouts, and was surprised and delighted to find that I had recently moved to within five miles of the headquarters of one of the major manufacturers. The sales rep recommended the product called Aqua Quench 365, and kindly gave me some to try.

To simplify things a bit, traditional quenchants are either water or oil. Water removes heat faster than oil, primarily by turning to steam. It is therefore a more severe quench than oil. This can induce distortion and cracking in armor because of the thin sections and the three dimensional shaping.

Oil quenchants are less severe, and in most ways better for armor work. There are two big drawbacks, though. The first is that the hot metal can ignite the oil, producing gouts of flame and clouds of smoke. The second is in the greasy mess that it leaves on the parts.

Aqueous polymers behave more like oil in their heat transfer characteristics, but with no flame and less mess.

Since giving up water quenches for aqueous polymers, I have had less warpage and no cracking.

Mac

[J.G.Elmslie]

Fascinating stuff.

I cant help but wonder how this would behave for quenching on really thin falchion blades. Going to have to see if I can find any UK manufacturers.

Thankyou, again, for the wealth of information in here.

[Mac]

They make a foil-laminated OSB sheet for radiant heat barriers under roofing. Your local big-box hardware store will likely have it. Might be more effective at resisting the heat than a sheet of plywood.

https://shop.mccoys.com/building-materi ... osb/p.2086

I was pretty excited about this, but it does not seem to be available in the greater Philly area.

Perhaps spray gluing aluminum foil to a sheet of masonite will do the trick. Does anyone here know how well spray glue handles heat?
Mac

[Keegan Ingrassia]

If you're using a spray adhesive, I'd recommend something automotive-grade, designed to bake in a parking lot for a decade or so and still hold on.

Looking around a bit, this seems to be a popular choice among restoration and gearhead folks.

DAP Weldwood, HHR Solvent, Spray Grade.

[Arrakis]

Wrap long strips around the wood and glue it on the back, away from the heat?

[Alex Baird]

Does anyone here know how well spray glue handles heat?
Mac

Like gasoline. Lots of VOCs in spray glue and rubber cement, and it burns.

[Mac]

Alex,

Is that your experience of it, even after it has had some time to finish outgassing its solvents? If so, then I certainly need to have a different idea.

Mac

[Keegan Ingrassia]

How about wood staples? Wrap the tin around to the back, and physically tack it in place.

[Mac]

I was thinking about staples. It would, I think, necessitate a heavier aluminum, and the substrate would probably have to be plywood, rather than masonite. Neither of those is a problem.

Mac

[Alex Baird]

Alex,

Is that your experience of it, even after it has had some time to finish outgassing its solvents? If so, then I certainly need to have a different idea.

Mac

It takes a long time to fully outgas all of the VOCs (weeks?), and after it does it remains, essentially, a distilled petroleum product. The dried stuff is still combustable (about like wood).
Here is the MSDS for 3M spray glue:http://multimedia.3m.com/mws/mediawebse ... D7SSSSSS--

Have you considered a cement board? Or whatever they use to line fireplace surrounds for gas inserts...

[Kristoffer]

On this side of the pond we have dense gypsym boards used in construction for improved fire protection. They are usually called "protect" but I believe that is a brand name. It can be used by itself since it is very strong and dense, or you can just screw it to boards or plywood.

[Chris Gilman]

Mac,
McMaster Carr has a number of thermal barrier panels if this is what you need. Also, they make "non-flammable" water based contact adhesives. Our Home Depot carries those, but then it's California and we can get the flammable kind.

[Mac]

I suspect that putting anything with a bit of thermal mass in between the kiln and the paper on the ceiling will do the trick. Paper and wood both kindle at the same temperature, but what will ignite paper immediately might take minutes to ignite (say) a sheet of masonite. The kiln will only be open for fifteen of twenty seconds.

When I first started heat treating in a kiln, I used to do it wearing a flannel shirt. I learned pretty early that if the sleeve plackets were not closed, I would get "sunburned" in ten or fifteen seconds. A couple of incidents where I tarried too long over the open kiln convinced me that I needed something fire retardant over the shirt. The smell of cotton on the edge of combustion is unmistakable and rather disconcerting when one is trying to manipulate an orange-hot helmet. I now wear one of those welding jackets when I reach into the kiln, and that seems to do the trick.

I think I will sling a sheet of masonite or plywood up over the kiln and do some experiments. My infra red thermometer should tell me if my shielding is getting hot enough to worry about. I'll keep the fire extinguisher handy.

Mac

[Sean Powell]

I was at Home Desperate earlier today. The sell foil-backed insulation in 4x8 sheets. It's made from Polyisocyanurate and is more fire resistant than the other insulation types. If I were trying to build a heat baffle I'd buy 2 sheets, screw it to 2 pieces of thin ply-wood with fender washers and long screws and then hang them from the rafters with wire. It avoids the whole glue burning issue entirely as they are using factory applied fire-resistant glue. The foil will help distribute heat over the insulation surface to avoid hot-spots. The insulation will keep the heat from penetrating to the support plywood. The hot air will spill upward and mix with regular air cooling before it hits the ceiling. If that won't cool it fast enough or long enough then you aren't blocking the heat and need a chimney instead.

It really doesn't matter how long the kiln is open. You have maybe 2x2x3= 12 sq-ft of super-heated air that needs to be dispersed when you open the lid. After that it's cold air going in, being heated enough to rise and then exiting to let more cool air in. Steady state should be nothing compared to the initial surge. Paper combustion is actually around 450C (Not F damn you Ray Bradbury) which is 842F. If you mix 12 cu-ft of 1870F air with 12 cu-ft of 70F air you get 24 cu-ft of 970 F air. You have a LOT more than 12 cu-ft of cool air to mix it with.

If you wanted to be fancy you could add 4 pieces of insulation to make a 4' deep inverted box which would hold 128 cu-ft of super-heated air until it cooled and flowed down or spilled upwards with more hot air added. If you wanted to be smart for the long term you could just insulate the ceiling with 1" R13 metalicised foam and call it done.

http://www.homedepot.com/p/Thermasheath ... /100549260

$20.25 per sheet is $0.68 per sq foot. Swagging you shop at 20x30 that's $406 to insulate the roof which will protect your building from the kiln and help keep the pewter studio warm in winter. Maye another $30 in for screws and washers. They actually sell them pre-assembled for hanging insulation (I think)

Sean

[Signo]

Just remember to : DO NOT SET YOURSELF ON FIRE.

[Mac]

I am all at loose ends about this heat treating thing at the moment. It took several iterations of filling, partial emptying and welding to deal with the porous places in my welds. I am trying to decide how much of my equipment to replace and with what...

--I have a line on stainless 55 gal drums in New Jersey for $160, and I think I will one.
--My current system involves warming the quench to about 100 F with a propane burner under the tank. That relies on a extra-tall dolly that Zanetto built for me.
--He also cut the current drum down to a convenient height.
--I'd like to get a larger volume of quenchant, but I don't want to edge of the tank much higher than it currently is.
--If I go with a taller tank and a lower dolly, I would need to get an electric tank heater.
--A new stainless drum will need to be opened and cut down some. The edge will need to be rolled for strength. I never work with stainless, so this will be an experience.
--If I try to run a kiln, a tempering range, and a drum heater all at the same time, I am taxing my electrical service. At least I wont have to heat the shop while that is happening.
--Meanwhile, I need to test whether or not the heat shielding I hung over the kiln is up to the task.
--I also need to see whether or not my old quenchant still does the job. The tech guys at Haughton suspect that the rust inhibiting chemistry will have either outgassed or been consumed by microbes while my brew was in storage. If they are right (and that's their job) my old steel tank will be rusting even faster than before.

Many things to think about. I need to plot a course and get going. I suppose I can achieve two objectives at once by trying to heat treat some of my scraps and castoffs. I'll keep the fire extinguisher(s) handy, and probably run the garden hose into the shop as well.

Mac

[Johann ColdIron]

I am all at loose ends about this heat treating thing at the moment. It took several iterations of filling, partial emptying and welding to deal with the porous places in my welds. I am trying to decide how much of my equipment to replace and with what...

--I have a line on stainless 55 gal drums in New Jersey for $160, and I think I will one.
--My current system involves warming the quench to about 100 F with a propane burner under the tank. That relies on a extra-tall dolly that Zanetto built for me.
--He also cut the current drum down to a convenient height.
--I'd like to get a larger volume of quenchant, but I don't want to edge of the tank much higher than it currently is.
--If I go with a taller tank and a lower dolly, I would need to get an electric tank heater.
--A new stainless drum will need to be opened and cut down some. The edge will need to be rolled for strength. I never work with stainless, so this will be an experience.
--If I try to run a kiln, a tempering range, and a drum heater all at the same time, I am taxing my electrical service. At least I wont have to heat the shop while that is happening.
--Meanwhile, I need to test whether or not the heat shielding I hung over the kiln is up to the task.
--I also need to see whether or not my old quenchant still does the job. The tech guys at Haughton suspect that the rust inhibiting chemistry will have either outgassed or been consumed by microbes while my brew was in storage. If they are right (and that's their job) my old steel tank will be rusting even faster than before.

Many things to think about. I need to plot a course and get going. I suppose I can achieve two objectives at once by trying to heat treat some of my scraps and castoffs. I'll keep the fire extinguisher(s) handy, and probably run the garden hose into the shop as well.

Mac

The tank edge rolling seems like a perfect job for a jenny if you have one that will do that stainless thickness. Even if you could get it rolled past 90* mechanically it would be a lot simpler task to hammer down.

I seem to remember band type heater for drums rather than from beneath which would allow you to get as low as possible. Most seem to be really expensive but I did find this http://www.ebay.com/itm/2x-ELECTRO-FLEX ... 2103624a08

[Aussie Yeoman]

Could you not wrap an electric blanket around the tank overnight? That's a cheap bit of hardware that doesn't require an open flame, and you can set the tank just as low as you please.

[Mac]

They make electric heaters for drums. I figured I would just break down and get one.



Mac

[Zanetto]

Mac,

I got an electric tank heater off of ebay for like $150. I works like a charm. I have to start it like 12 hours before I plan to heat treat to get it to temperature, but that is not usually a problem.

Rob

[Sean Powell]

Electric heater seems like the best choice but if there is a side 'bung hole' in the barrel you might be able to add some pipe sections and heat the liquid externally.

Sean

[Mac]

Here's the set up as it currently is. I built this 4'x4' heat shield out of masonite and 1x4s and hung it from the ceiling joists with light chain and screw eyes. I am pretty confident of masonite's ability to deal with heat. I have used it in direct contact with molten tin and it barely gets a suntan.



With that in place, I did a little test today. I had two different fire extinguishers at hand, as well as the garden hose in case my heat shield burst into flame. I also had my infra red thermometer ready to measure the temperature of the masonite after the kiln was opened.

I turned the kiln on "low" for an hour or so and then turned it to "high" for a couple of hours. That's when things got weird. My pyrometer came up to about 500f and would not go higher. After a bit I lifted the lid and was surprised to see everything orange inside. Clearly it was hotter than 500. I then tapped the gauge repeatedly to see if that would free the needle. It did, but instead of settling at some reasonable temperature, it kept rising as long as I kept tapping until it came to rest at somewhere around 2200f. ....and you know that ain't right either.

(sorry about the focus)


Well... nothing burst into flame. In fact, the heat shield never got any hotter than about 110f. It's almost disappointing after all that preparation and fretting. I suspect that the heat shield is unnecessary, but I will keep it in place until I have more experience with this setup.

Since the kiln looked to me like about 1550f or so from the color, I figured I would try to harden something. I did not have anything prepared, because the faulty pyrometer had me thinking I had plenty of time to rig something. I quickly punched an extra hole in a scrap vambrace and wired it up.

I can only guess at the hardening temperature, but it did harden OK. Here is a pic of it in the shop oven to "take the edge off" at 350f for a few minutes



I will not try to temper it for real till I get my pyrometer fixed or replaced.

Jeremy will recognize this. He put some of the flutes in it a couple of weeks ago.



Tomorrow, when the kiln is cool, I will remove the pyrometer gauge and see if I can find a problem with the needle pivots. When I first bought this kiln back in 2001, the needle had jammed in its pivots from rough handling. Since this is the first time I have asked it to do anything since moving shop, I hope it's the same thing again. If so, 'tis an easy fix.

Mac

[Mac]

This morning I drove to a gritty industrial area of Camden NJ's waterfront to get a stainless steel drum to turn into a quench tank. This is a place where the city allows their streets to be impassably blocked by semitrailers and stacks of drums. The fellow I spoke to said that its been like that since the 60s. I could see from the satellite view on GoogleMaps that some of the roads were impassable, but since that photo was taken, the trailers have been re-parked to block different places. Needless to say my Garmin was flummoxed. After going around the block a few times, I turned into an alleyway with a street name and that got me where I needed to be.

It was a bit surreal, and I am glad to be back with my treasure.



Mac

[RandallMoffett]

Neat find but sounds like the place is a bit odd. I am glad you did not find your path blocked as you were leaving...

[Mac]

This evening, I started looking into the faulty prometer. I got as far as backing the first sheet metal screw out of the expanded mesh that forms the front of the kiln's electrical control box when it occurred to me that I really needed to unplug this thing.



I pulled the gauge out and laid the hardware out on top so I would not loose anything.



By the time I had the gauge in hand, the needle had returned to the low end of the scale. As I played with it, I saw that sometimes the needle was free to move, and other times it stuck



In a bit the problem became obvious. The glass had become detached at the top and was jamming the needle.



This explains the observed problem so well, that there does not seem to be any point looking further. The gauge must have gotten damaged in moving the kiln from the old shop. I just need to get the glass fastened back in place and reinstall the gauge.

First, though, I needed to figure out how the glass was supposed to be held in place. To do that, I took it upstairs to the watch bench and took the three brass screws out of the back of the case. Two of the screws are visible here along the bottom and the third is obscured by the gauge body.



Having removed the glass completely, I saw that it had been held in by a bead of black silicone sealer.



The old silicone had held pretty well to the glass...



...but not so well to the smooth plastic of the case.



I have taken this opportunity to roughen up the inside of the case with some sandpaper to improve the adhesion. The original silicone held OK on the smooth Bakelite since the mid 70s. I would be surprised if this repair did not outlive me.



Tomorrow I'll get some fresh silicon sealer from the Home Despot and glue the (now clean) glass back in place. I won't be able to get black, but that's OK.

Mac

[Jeremy.G]

You've been busy! I'm glad to see your heat-treat setup is almost operational again, and didn't take tons of work to get it there.

[Johann ColdIron]

Tomorrow I'll get some fresh silicon sealer from the Home Despot and glue the (now clean) glass back in place. I won't be able to get black, but that's OK.

Mac

You should be able to get black silicone. I've used it on some roof repairs.

Problem is you will have to buy way more than you need for this project, even getting the smallest tube. So I would be tempted to buy clear and use the rest on some house caulking project. It never seems to last once the tube is opened.

Or does it need to be high temp stuff? Then an Auto supply store will have something suitable (and black).