exothermic ( thermite ) welding

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peace

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hello all,

I am working with exothermic ( thermite ) welding and I need to know more about this subject so cold you provide me with standards, articles or books ?

thanks
 
one important safety note: molten metals and water no not mix. If there is any doubt that the mold is completely dry, dry it with an electric heat gun- propane torches have moisture in the flame. I had a friend who got burned many years ago using one of the molds first thing in the morning, it was cold and had condensation on it
 
I do not believe a heat gun will produce enough heat to dissipate the moisture in the steel, mold, or other material.

I spent a winter - freezing rain and snow at no extra charge - cadwelding impedance bonds to railroad tracks.
pwrbond.jpg

We used propane (maybe MAPP???) tanks. 99% of the welds were good on the first shot. You need a lot of heat to remove the moisture from a rail! The same gas also made short work of heating/removing moisture from the molds.


A few tips:
Before shooting the weld, pack the exterior edges with duct seal. If for some reason the mold is not completely seated, the material will come right out, and erupt on impact.

Don't breathe in the smoke...either get your face out of the way or pay attention to which way the wind is blowing.

Keep a fire extinguisher or sand handy. If the material escapes, it WILL ignite other objects.

A grinder. If the object you are welding to is not clean - you will be shooting it again...after you clean off the first "opps". A cold chisel and a lump hammer work for "tight" spots (saftey glasses/goggles too).

Welding gloves. Depending on the size and/or number of welds you plan on doing, these might be a must. Don't use ANY gloves that can ignite (ie, cotton) or "shrink" when heated (ie, ANY rayon, polyester, etc blends)

If you run out of "pennies", a piece of paper will suffice (on large shots, I wouldn't reccomend it on small shots)..but don't make it a habit.

Try a few "dry runs". Create an ideal situation and give it a go.

Visit the [Erico Site] (Cadweld is one of their brands):



A work of CAUTION:

Keep a first aid kit handy

I had a guy who had never welded work with me one summer...I told him the molds will be EXTREMELY hot after shooting them - DO NOT TOUCH THEM. Well, he reached over one (hot) mold to grab a cool one and now has a nice square burn mark on his forearm....thankfully, we had the first-aid kit with us.
 
RUWired said:
Here is a picture of a cad weld in progress.
NICE!

Things to take notice of:
- The smoke plume - not in anyone's face, but the "kid" is gonna need to move soon :)
- Wood under the mold...it the mold spills, sure the wood may go on fire but at least there will be no "eruption".
-Gloves..hands properly protected.
- Scorch marks on wood...you can see where they had a little spillage...usually not a big deal.


One of these days, before the alhimzers' really sets in, I'll remember to bring a camera to the jobsite.
 
celtic said:
I do not believe a heat gun will produce enough heat to dissipate the moisture in the steel, mold, or other material.

I've never had to dry the materials, just been real careful about the molds being good and dry. I have used a torch to dry them before, I'd heat it then wait a little, but always felt better with the electric heat.

BTW, is there a better test for a weld than the old 'smack it with the hammer'?
 
Whatever you are welding TO must also be moisture free.

I heated up the ends of a few of the bonds, I could tell no difference after all was said and done.

test...maybe x-ray it?
Smacking it with a big ol' lump hammer (although rather neantherthal) seems to work - coupled with a visual inspection to check the "quality" of the "nugget".
 
Four years ago, we got a job doing the ground (geographically and electrically speaking) work on a cell site at the base of a transmission-line-tower-mounted cellular antenna array.

With a 5/8" copper rod every 10' along the (tinned solid #2 copper) ground ring, bonding adjacent metal parts, along with multiple taps to every piece of metal (BTL platform, power cabinet posts, cable racks, nearest tower legs' ground wires, etc.), we did a lot of Cad-Welds.

It was also the job that (finally!) justified buying our Bosch rotary hammer and rod-driver bits. No more fence-post drivers and sledge hammers!

Here's a few click-to-enlarge pics:

PVC bringing power cabinet's EGC and post bonding to the ground ring:


A tap off of the ring to one corner of the BTL platform:



A weld to the platform, enclosed in 1/2" FNMC and silicone'd:


A close-up of a ring-to-rod weld in one of two test-welds:



By the way, a friend and I decided to weld two lengths of the #2 together and then saw through the weld. You can not tell where the conductors' surfaces meet the welded material; it appears to be one homogenous mass.
 
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LarryFine said:
By the way, a friend and I decided to weld two lengths of the #2 together and then saw through the weld. You can not tell where the conductors' surfaces meet the welded material; it appears to be one homogenous mass.

Once you have a little experience with these things...you start to get creative...LOL - keep the 1st aid kit handy!
 
Does erico sell molds for say 2-5 #12 conductors? Ya know so that I can weld splices that I would otherwise have to solder......

*grin*

-Jon

(seriously: no offence intended to the idea of soldering splices if that is what the customer wants and is willing to pay for...but if they want solder, why not go all the way to welding ....)
 
winnie said:
Does erico sell molds for say 2-5 #12 conductors? Ya know so that I can weld splices that I would otherwise have to solder......

*grin*

-Jon

(seriously: no offence intended to the idea of soldering splices if that is what the customer wants and is willing to pay for...but if they want solder, why not go all the way to welding ....)

Check out this picture:

RUWired said:

You really want to set that off inside?
 
celtic said:
You really want to set that off inside?

It depends.....how nice is inside?
icon10.gif


Did anyone see "Extreme Engineering" when they where 'Cad welding' railroad tracks?

Velp-thermitewelding-1.jpg


Makes our 150 shots look like sparklers.

Edit: add photo
 
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CadWeld uses a thermite material or powered aluminum, used in WWII to burn thru concrete bunkers. A coworker was doing a 750 shot in a teleco office and it leaked thru the mold and burnt a hole in the concrete floor.
Compression is much easier for smaller conductors!
 
iwire said:
It depends.....how nice is inside?
icon10.gif


Did anyone see "Extreme Engineering" when they where 'Cad welding' railroad tracks?

See it?

I was THERE - not at that show or with those people, but in a former job I watched the "Track Dogs" do their thing on "hi-speed" rail....no breaks in the rail for about a mile!

They had a special grinder all rigged up (probably a manufacutered tool) to grind the rail smooth after shooting it. It looked like some sort of a sheetrock dolly (A-Frame) with wheels to ride the rail and a grinder mounted below. They could angle the grinder any which way they needed it to be.

The sections of rail were brought to the site...by rail...LOL...long long lengths, not the normal 63' +/- lengths (an old timer gave me the number)....so long that when they dragged them down the right of way, the tail end would whip about like a garden hose (a clue to slow down before someone was killed or equipement damaged).

That is some tremedous shot.
 
celtic said:
They had a special grinder all rigged up (probably a manufacutered tool) to grind the rail smooth after shooting it. It looked like some sort of a sheetrock dolly (A-Frame) with wheels to ride the rail and a grinder mounted below. They could angle the grinder any which way they needed it to be.

Kind of like this?

FG10-Studio.jpg
 
CADWELD has a new electric ignitor, with this the shots are enclosed, and disk and powered is combined into one. The shots are the same cost as the powder, so the extra cost is for the ignitor. I have big box with all the shots, files, duct seal, gloves, etc. I keep a welding hammer to chip off the slag.
I also have a self igniting propane torch to dry the mold. Erico (Electric Railway Improvement Co) invented cadweld for railroads in the 1930's?, states you can cadweld in wet and rain, but I wouldn't.
Also Erico has good tech support and training videos available. The big disadvantage is each wire size and type of attachement requires a seperate mold. I only do one size wire (#2) so have several handles. I have a magnetic handle for welding to steel tanks, and a chain handle for 2" pipes.
 
tom baker said:
Erico (Electric Railway Improvement Co)
....I didn't know that....



tom baker said:
states you can cadweld in wet and rain, but I wouldn't.
You CAN...you can also go swimming with cement boots.

I had attempted to weld in rain - it's a disaster. We "built" a tent out of blue tarps and EMT to shield us and the welding act....another time I should have brought a camera :mad:

Now as far as the swimming with cement boots....just ask anyone from NYC about that ;)
 
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