Western Railroad Discussion > Thermite

Is a thermited joint in the rail a weak point or is it stronger than steel?

Was watching one such joint going through some good flexing under the train wheels.  

Watching a crew thermite is always impressive like a miniature volcano going on.  

Chuck 

If it is done correctly it's as strong as the rest of the rail as shown in the first photo.
Second photo shows a bad weld that broke after about a week of service.

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Looks strange is that white paint or just a bad picture?  First one just look like bad rail that needs to be replace second one for some reason part of the weld parted the rest just a cold weld to part of the rail. Just suggesting am sure someone knows more about it and how wide a gap can be welded that way?  

BAB Wrote:
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> Looks strange is that white paint or just a bad
> picture?  First one just look like bad rail that
> needs to be replace second one for some reason
> part of the weld parted the rest just a cold weld
> to part of the rail. Just suggesting am sure
> someone knows more about it and how wide a gap can
> be welded that way?  

Looks to me like snow, both behind and in front. The gray on either side of break, well, justa result of the weld itself? Like flashing.  Ben

Schnow...LOL

Snow huh, bad preheat around the weld point, usually not an issue in more temperate weather.

Out 

Even the best thermite welds upset the work-hardened running surface of the rail, they anneal it.
After a few million tons of traffic this will become a small depression, until the new metal is as hard as the parent metal.
The next rail grinding train should level things out.
This becomes noticable when the track is otherwise in excellent conditon, especially for high speed passenger operations.

BAB Wrote:
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> Looks strange is that white paint or just a bad
> picture?  First one just look like bad rail that
> needs to be replace second one for some reason
> part of the weld parted the rest just a cold weld
> to part of the rail. Just suggesting am sure
> someone knows more about it and how wide a gap can
> be welded that way?  
That is snow and the weld is maybe a week old and broke. It was at night and took the best photo I could get. They spliced a new short piece of rail in there and was welded a week later and has been good ever since.

Posted from iPhone

Thermite weld being done during the reconstruction of Illmon Canyon on Tehachapi, 1984.
—Mac

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MacBeau Wrote:
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> Thermite weld being done during the reconstruction
> of Illmon Canyon on Tehachapi, 1984.


Send that to one of the Chicago media that shows a picture of gas switch heaters with a story about setting the track on fire because of snow.

TAW

TAW Wrote:
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> MacBeau Wrote:
> --------------------------------------------------
> -----
> > Thermite weld being done during the
> reconstruction
> > of Illmon Canyon on Tehachapi, 1984.
>
>
> Send that to one of the Chicago media that shows a
> picture of gas switch heaters with a story about
> setting the track on fire because of snow.
>
> TAW

Not just the Chicago media...

Question Mike (and others): What makes for a bad thermite weld?  Contamination?

railstiesballast Wrote:
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> Even the best thermite welds upset the
> work-hardened running surface of the rail, they
> anneal it.
> After a few million tons of traffic this will
> become a small depression, until the new metal is
> as hard as the parent metal.
> The next rail grinding train should level things
> out.
> This becomes noticable when the track is otherwise
> in excellent conditon, especially for high speed
> passenger operations.

Yes contamination ie not cleaning the joining surfaces, heat issue due to a bad
ie cool or cold joint in which the burn isn't complete and a big temperature difference
between the weld area and the adjoining rail.

Out 

ns2557 Wrote:
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>
> Looks to me like snow, both behind and in front.
> The gray on either side of break, well, justa
> result of the weld itself? Like flashing.  Ben

Ben, your probably right and I agree with seeing the snow in front and back of rail, but I bet they decided to use a gray filler material like "JB Weld" that broke away.  Ha, Ha!!!!!  
And April 1st ain't here yet!!



Edited 2 time(s). Last edit at 02/12/24 14:01 by rrman6.

Can thermiting be done on say 10 degree F rail or are there temperature limits?

Curious if a break/gap can't be thermited for whatever reason then holes have to be drilled in the rails and joint bars installed?

Those rails are some high-quality steel it's amazing how MOW does their job.  

Chuck 

The rail ends to be welded are heated with an acetylene torch first. 
—Mac

RailDawg Wrote:
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> Can thermiting be done on say 10 degree F rail or
> are there temperature limits?
>
> Curious if a break/gap can't be thermited for
> whatever reason then holes have to be drilled in
> the rails and joint bars installed?
>
> Those rails are some high-quality steel it's
> amazing how MOW does their job.  
>
> Chuck 

Thanks Mac makes sense.  

Did not know that. 

Do the rail-ends have to be like red-hot before the thermite does it's thing?

Chuck 

Not glowing like fresh out of the rolling mill, but hot enough to not cause a fissure in the weld.
—Mac

RailDawg Wrote:
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> Thanks Mac makes sense.  
>
> Did not know that. 
>
> Do the rail-ends have to be like red-hot before
> the thermite does it's thing?
>
> Chuck 

I know how it works but I am always amazed that it (normally) results in quality steel. And yet it does.