There is another welding process called Thermite welding. It is also known as exothermic welding

It is used in the railway industry to weld long sections of rail.

Basically you lay the two rails butting them up against each other.

You then build an empty "volcano with heat resistant putty.

You then fill this "volcano" with Iron oxide and aluminium powder.

You then ignite the powder mix.

The aluminium and iron oxide react very violently to then become Aluminium oxide and iron. The huge amount of heat also melts the two rail ends together.

Another powder combination can be used, copper oxide and aluminium. for the formation of electrical joints.

When the reaction is proceeding, it does look like a volcano.....

After its all cooled down, apply angle grinder till you have a continuous rail with no perceptible joint... and hence no clackety clack of train carriage wheels over the rail joint.....

wrote in message
...

There is another welding process called Thermite welding. It is also known
as exothermic welding

It is used in the railway industry to weld long sections of rail.

Basically you lay the two rails butting them up against each other.

You then build an empty "volcano with heat resistant putty.

You then fill this "volcano" with Iron oxide and aluminium powder.

You then ignite the powder mix.

The aluminium and iron oxide react very violently to then become Aluminium
oxide and iron. The huge amount of heat also melts the two rail ends
together.

Another powder combination can be used, copper oxide and aluminium. for the
formation of electrical joints.

When the reaction is proceeding, it does look like a volcano.....

After its all cooled down, apply angle grinder till you have a continuous
rail with no perceptible joint... and hence no clackety clack of train
carriage wheels over the rail joint.....


Yes it's a very impressive process to watch 'up close and personal'

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates' deliberately
leave an expansion gap to allow for this. Now unless the EU has banned
thermal expansion it presumably still happens. I was told as one explanation
that rails are 'stretched' before joining but have seen no evidence of this
watching thermite welding being done and the forces involved would be
immense. Maybe modern rails are made of Invar - I think not

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components


Andrew

On Sat, 26 Apr 2014 09:11:18 +0100 Andrew Mawson wrote :
Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates' deliberately
leave an expansion gap to allow for this. Now unless the EU has banned
thermal expansion it presumably still happens. I was told as one explanation
that rails are 'stretched' before joining but have seen no evidence of this
watching thermite welding being done and the forces involved would be
immense. Maybe modern rails are made of Invar - I think not

Yes, rails will expand in the heat, but the expansion doesn't have to be
linear. If the rails are firmly held in position and the length is fixed,
the expansion will translate into an enlarged cross section - think of
holding an eraser between thumb and finger - if you squeeze it, it bulges
out.

http://en.wikipedia.org/wiki/Rail_stressing

But because on very hot days there is a huge compressive stress in the
track, if something gives the effect can be pretty dramatic

http://www.couriermail.com.au/questn...-1226531550617

--
Tony Bryer, Greentram: 'Software to build on',
Melbourne, Australia www.greentram.com

On 26/04/2014 01:04, Cursitor Doom wrote:
There is also a very primitive form of welding which basically
involves beating the living **** out of two bits of metal until they
have no alternative but to fuse together. You don't need a filler for
this process; just arms like Popeye.

No, you just need a striker with arms like Popeye.

Colin Bignell

Yes it's a very impressive process to watch 'up close and personal'

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates' deliberately
leave an expansion gap to allow for this. Now unless the EU has banned
thermal expansion it presumably still happens. I was told as one explanation
that rails are 'stretched' before joining but have seen no evidence of this
watching thermite welding being done and the forces involved would be
immense. Maybe modern rails are made of Invar - I think not

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components


And laser welding. I had a detached retina re affixed by around 130
shots of an Argon laser over the space of three minutes a few years
ago;!...

Suppose I'd be blind on one eye if that tech wasn't around...
--
Tony Sayer

On Sat, 26 Apr 2014 13:34:56 +0100, tony sayer
wrote:


Yes it's a very impressive process to watch 'up close and personal'

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates' deliberately
leave an expansion gap to allow for this. Now unless the EU has banned
thermal expansion it presumably still happens. I was told as one explanation
that rails are 'stretched' before joining but have seen no evidence of this
watching thermite welding being done and the forces involved would be
immense. Maybe modern rails are made of Invar - I think not

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components


And laser welding. I had a detached retina re affixed by around 130
shots of an Argon laser over the space of three minutes a few years
ago;!...

Suppose I'd be blind on one eye if that tech wasn't around...

Hopefully not so. When I had my retina refixed back in the early
eighties it was cryogenic welding with a probe that was inserted
through the white of the eye. My retina got "creased" in the process
and it took some time before my brain learned that straight lines
weren't wavey. Hopefully yours was refixed a little better than that
though, to be fair, back in those days I was just grateful that I
could see through that eye again.

Nick

In article , Nick Odell
scribeth thus
On Sat, 26 Apr 2014 13:34:56 +0100, tony sayer
wrote:


Yes it's a very impressive process to watch 'up close and personal'

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates' deliberately
leave an expansion gap to allow for this. Now unless the EU has banned
thermal expansion it presumably still happens. I was told as one explanation
that rails are 'stretched' before joining but have seen no evidence of this
watching thermite welding being done and the forces involved would be
immense. Maybe modern rails are made of Invar - I think not

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components


And laser welding. I had a detached retina re affixed by around 130
shots of an Argon laser over the space of three minutes a few years
ago;!...

Suppose I'd be blind on one eye if that tech wasn't around...

Hopefully not so. When I had my retina refixed back in the early
eighties it was cryogenic welding with a probe that was inserted
through the white of the eye. My retina got "creased" in the process
and it took some time before my brain learned that straight lines
weren't wavey. Hopefully yours was refixed a little better than that
though, to be fair, back in those days I was just grateful that I
could see through that eye again.

Nick


Well I did think it odd that the insultant said "just go get some lunch
and come back and we'll operate then" had visions of something like
that;!..

Has worked very well, have a check-up every so often and thus far no
problems..

Vision good enough corrected to be a commercial airline pilot so I'm
told and uncorrected just scrapes by the road number plate as tested
recently by a traffic policeman on a sight test demo..

And Do I always remember the glasses when cutting that bit of steel
sometimes .. course it'll be alright won't it;()
--
Tony Sayer

On 24/04/2014 08:08, Andrew Mawson wrote:
"Nightjar" wrote in message
...



nope, not an academic... I'm a materials technologist.

That sounds like a very academic discipline to me.


Could just be the storeman who says 'nah - not EN8, I'd use a bit of
brass, mate '

Do I detect a certain amount of cynicism about modern job titles?

Colin Bignell


Oh yes !
It started when Dustmen became 'Cleansing Operatives' then arty farty
types get together for 'workshops' and countless other examples of
avoiding calling a spade a spade

Andrew



Six weeks ago I couldn't even spell engineer - now I are one.

--
mailto:news{at}admac(dot}myzen{dot}co{dot}uk

On Sat, 26 Apr 2014 09:11:18 +0100, "Andrew Mawson"
wrote:

I was told as one explanation
that rails are 'stretched' before joining but have seen no evidence of this
watching thermite welding being done and the forces involved would be
immense

I haven't seen the welding being done but have worked in possessions
where the rail clips are removed and every 5th one replaced by a
roller which fits under the top "web" of the rail, it's an over centre
device operated by rotating a square nut through 90 degrees so the
rail is clear of the sleeper and free to roll on this "pandrol
destresser". I have one on my desk picked up by a litter patrol.

As I have not noticed any expansion devices recently I assumed that
all the expansion was taken up by the spring in the stressed rail.

AJH

On 26/04/2014 09:11, Andrew Mawson wrote:
wrote in message
...

There is another welding process called Thermite welding. It is also
known as exothermic welding

It is used in the railway industry to weld long sections of rail.

Basically you lay the two rails butting them up against each other.

You then build an empty "volcano with heat resistant putty.

You then fill this "volcano" with Iron oxide and aluminium powder.

You then ignite the powder mix.

The aluminium and iron oxide react very violently to then become
Aluminium oxide and iron. The huge amount of heat also melts the two
rail ends together.

Another powder combination can be used, copper oxide and aluminium.
for the formation of electrical joints.

When the reaction is proceeding, it does look like a volcano.....

After its all cooled down, apply angle grinder till you have a
continuous rail with no perceptible joint... and hence no clackety
clack of train carriage wheels over the rail joint.....


Yes it's a very impressive process to watch 'up close and personal'

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates'
deliberately leave an expansion gap to allow for this. Now unless the EU
has banned thermal expansion it presumably still happens. I was told as
one explanation that rails are 'stretched' before joining but have seen
no evidence of this watching thermite welding being done and the forces
involved would be immense. Maybe modern rails are made of Invar - I
think not

I was under the impression they had a type of scarf joint ever so often
that was not welded and this was to absorb the expansion...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 26/04/2014 09:11, Andrew Mawson wrote:

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates'
deliberately leave an expansion gap to allow for this. Now unless the EU
has banned thermal expansion it presumably still happens. I was told as
one explanation that rails are 'stretched' before joining but have seen
no evidence of this watching thermite welding being done and the forces
involved would be immense. Maybe modern rails are made of Invar - I
think not

They have extremely effective devices, effectively a form of jack, for
applying tension to the rails - but that will be up or down the track a
bit from the site of the thermite weld.

Can't now remember the temperature they aim for, think it is what the
rails get to on a warm, sunny day (rather than extreme hot day). When
that temperature is reached, the rail will have close to zero tension,
if temperature continues to rise, they can and do end up in compression.

Buckling can occur if they get it wrong!

--
Rod

On Thu, 24 Apr 2014 21:38:19 +0100, tony sayer
wrote:

In article , Andrew Mawson
scribeth thus

(* my first soldering was using a copper bit heated on the gas ring making a
crystal set when I was 9, and yes it did work )

Close to an MF TX then as mine didn't;(..

Did the same thing myself at the same age and was utterly euphoric at
immediately picking up a stentorian voice conveying round the clock
news with astounding clarity and no fading whatsoever. I was less
chuffed when I eventually discovered that was *all* I could receive
over the entire tuning range and it was in fact the BBC World Service
(1MW DC input power) less than 3 miles away. Could have picked the
damn thing up on a loose filling.

In article ,
polygonum writes:
On 26/04/2014 09:11, Andrew Mawson wrote:

Thing that puzzles me is when a rail is joined to the next there is no
allowance for thermal expansion. Rails joined by 'fishplates'
deliberately leave an expansion gap to allow for this. Now unless the EU
has banned thermal expansion it presumably still happens. I was told as
one explanation that rails are 'stretched' before joining but have seen
no evidence of this watching thermite welding being done and the forces
involved would be immense. Maybe modern rails are made of Invar - I
think not

They have extremely effective devices, effectively a form of jack, for
applying tension to the rails - but that will be up or down the track a
bit from the site of the thermite weld.

Can't now remember the temperature they aim for, think it is what the
rails get to on a warm, sunny day (rather than extreme hot day). When
that temperature is reached, the rail will have close to zero tension,
if temperature continues to rise, they can and do end up in compression.

Buckling can occur if they get it wrong!

They start failing (buckle) at around 35C summer temperature.
The rails themselves are probably hotter in the sun when this
happens, but that's about the ambient temperature when lines
start being closed. I only recall it happening a small number
of times.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Sat, 26 Apr 2014 19:04:23 +1000, Tony Bryer
wrote:

Yes, rails will expand in the heat, but the expansion doesn't have to be
linear.

Are you sure about that? When I was at school (long, long, long time
ago) and doing my O levels, we had to learn about something called the
"coefficient of linear expansion" which states, if I recall correctly
(maybe I don't, it was a LONG time ago (if I haven't already mentioned
that)) that linear expansion is inevitable in certain materieals and
is directly related to temperature (rails fall within that category of
"materials").

In article , Andrew Mawson wrote:

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components

I've seen it used for fairly sizable chunks of lithium-aluminium alloy,
which is difficult to weld using conventional means :-)

Also friction welding, which will do fun things like let you weld[1] copper
to steel.

[1] or technically not weld, depending on your precise definition....

On 23/04/2014 18:36, Stephen wrote:
On 23/04/2014 18:09, John Williamson wrote:



well "hard soldering" may well be the old fashioned name for brazing but
I can assure you that the difference between brazing and soldering
relates to the process temperature rather than the hardness of the
filler metal.

When I was studying metalwork mumblety years ago, there were four ways
of joining metal involving heat.

Welding - With or without filler rod. I never did get the trick of it.
:-/

Brazing - Brass filler rods with Borax flux when joining steel or iron.
My preferred option if a reasonable joint strength was needed.

Silver Soldering - Similar to brazing, with a similar flux, but using a
silver alloy with a lower melting point than brass. For when the
blowlamp couldn't get the metal hot enough to braze, or the parent metal
was something like copper, with a lower melting point than the brazing
rods. Handy for model steam engine boilers.

Soft soldering - Using a lead/ tin alloy with either an acid or rosin
based flux, depending on what was being joined. The solder varied from
what was known as Tinman's solder (Almost pure tin) to almost pure lead,
but was mostly near the 63/37 eutectic mixture. The heating varied from
a tiddly little electric iron to a flamin' great blowlamp, via a half
pound copper bit heated in a gas oven on the workbench until the gas
flame was just tinged slightly with green.


I'm obviously considerably younger than you then, I trained in materials
science to masters and doctoral level in late 1990's early 2000's....
What you describe sounds very 1960's or 1970's......

joining technology has moved on considerably since then!

Sure, plenty of *new* methods. Few of them applicable in a shed with
basic equipment, though. And there's nothing wrong with the old methods,
done properly.

On 27/04/2014 22:35, Cursitor Doom wrote:
On Sat, 26 Apr 2014 19:04:23 +1000, Tony Bryer
wrote:

Yes, rails will expand in the heat, but the expansion doesn't have to be
linear.

Are you sure about that? When I was at school (long, long, long time
ago) and doing my O levels, we had to learn about something called the
"coefficient of linear expansion" which states, if I recall correctly
(maybe I don't, it was a LONG time ago (if I haven't already mentioned
that)) that linear expansion is inevitable in certain materieals and
is directly related to temperature (rails fall within that category of
"materials").

All that is still true... and keep in mind that linear expansion will
happen along all three axis.

The question is then what happens if you *constrain* the expansion along
one axis?

You get a similar effect to if you attempted to compress a rail along
its length while preventing it from bending - i.e. it will get fatter in
width and height and shorted in length.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:

All that is still true... and keep in mind that linear expansion will
happen along all three axis.

The question is then what happens if you *constrain* the expansion along
one axis?

You get a similar effect to if you attempted to compress a rail along
its length while preventing it from bending - i.e. it will get fatter in
width and height and shorted in length.

Whilst theoretically true, in the context being discussed the
reality is that the constraining forces would have to be
impractically large.

Chris
--
Chris J Dixon Nottingham UK


Plant amazing Acers.

On 28/04/2014 15:39, Chris J Dixon wrote:
John Rumm wrote:

All that is still true... and keep in mind that linear expansion will
happen along all three axis.

The question is then what happens if you *constrain* the expansion along
one axis?

You get a similar effect to if you attempted to compress a rail along
its length while preventing it from bending - i.e. it will get fatter in
width and height and shorted in length.

Whilst theoretically true, in the context being discussed the
reality is that the constraining forces would have to be
impractically large.

I have not done the sums, but if you start with the rails in tension (as
they do) - so they are somewhat stretched at lower temperatures, then
relax as it warms, before finally ending up in compression. I would have
thought the restraining force you could achieve with solid fixings to
hundreds of concrete sleepers would be fairly significant. (and no need
to resist all movement since there are/can be expansion joints as well).



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article , Alan Braggins wrote:
In article , Andrew Mawson wrote:

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components

I've seen it used for fairly sizable chunks of lithium-aluminium alloy,
which is difficult to weld using conventional means :-)

Sorry, it was magnesium-lithium. It was years ago.

On 29/04/2014 09:22, Alan Braggins wrote:
In article , Alan Braggins wrote:
In article , Andrew Mawson wrote:

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components

I've seen it used for fairly sizable chunks of lithium-aluminium alloy,
which is difficult to weld using conventional means :-)

Sorry, it was magnesium-lithium. It was years ago.


welding of magnesium - lithium poses special challenges as both are
extremely reactive metals..........

In article , Stephen wrote:
On 29/04/2014 09:22, Alan Braggins wrote:
In article , Alan Braggins wrote:
In article , Andrew Mawson wrote:

Next welding topic : 'Electron Beam Welding' - not welding two beams of
electrons together, but using a beam of electrons in a vacuum to fuse metals
in (usually) very small components

I've seen it used for fairly sizable chunks of lithium-aluminium alloy,
which is difficult to weld using conventional means :-)

Sorry, it was magnesium-lithium. It was years ago.

welding of magnesium - lithium poses special challenges as both are
extremely reactive metals..........

Thank you, Captain Obvious.

"Alan Braggins" wrote in message
...

In article , Stephen wrote:
On 29/04/2014 09:22, Alan Braggins wrote:
In article , Alan Braggins
wrote:
In article , Andrew Mawson
wrote:

Next welding topic : 'Electron Beam Welding' - not welding two beams
of
electrons together, but using a beam of electrons in a vacuum to fuse
metals
in (usually) very small components

I've seen it used for fairly sizable chunks of lithium-aluminium alloy,
which is difficult to weld using conventional means :-)

Sorry, it was magnesium-lithium. It was years ago.

welding of magnesium - lithium poses special challenges as both are
extremely reactive metals..........

Thank you, Captain Obvious.

It had to be said !!!!



Andrew

Have to admit I did notice lithium was a bit on the volatile side when
a teacher I once knew dropped a knob of it in a beaker of water,
blowing it to bits.

Anyway, I have a likely candidate for a brazing torch which I picked
up today in BnQ. It's this one:

http://www.diy.com/nav/fix/handtools...skuId=11758762

It has an appreciably finer flame than the torch I use for soldering
pipes, so I'm hopeful it will do the trick for brazing. I don't think
I'll do any better without oxy setup which is too much for my modest
requirements.

On 29/04/2014 21:51, Cursitor Doom wrote:

Have to admit I did notice lithium was a bit on the volatile side when
a teacher I once knew dropped a knob of it in a beaker of water,
blowing it to bits.


you have reminded me of an incident at my mother's workplace which was a
school where she was a cleaner.

The Chemistry teacher held a lesson demonstrating the reactivity of
various metals such as sodium, potassium, phosphorus, Magnesium, lithium
etc.

Two school boys decided to play a prank on one of the school cleaners....

They stole the phosphorus from the lab. Phosphorus is so reactive its
kept under oil within its container.

They went to the boys toilets, poured some oil onto the toilet taking
into account that oil floats on water. put some toilet paper on top of
the oil layer, then put the phosphorus onto the toilet paper. (the
toilet paper was needed to stop the phosphorus from dropping through the
oil into the water underneath and the oil was used as a barrier between
the phosphorus and the water.

For good measure they dropped a couple of no 2's in, m aking sure no
intimate contact was made with the phosphorus as the No 2's contain
small amounts of moisture.

The last bell of the day went, and the pupils went home.

One of the cleaners went into the boys toilets to do the dialy cleaning
ritual. She went into one of the cubicles, spotted that someone had not
flushed the loo after their no 2's. So she pulled the flush.

There was a almighty flash in the pan, tempoarily blinding her and the
reaction was so fierce that it set fire to the toilet paper and
shattered the pan.

Needless to say the two school boys were identified and expelled.....

On 29/04/2014 21:51, Cursitor Doom wrote:

Have to admit I did notice lithium was a bit on the volatile side when
a teacher I once knew dropped a knob of it in a beaker of water,
blowing it to bits.

Anyway, I have a likely candidate for a brazing torch which I picked
up today in BnQ. It's this one:

http://www.diy.com/nav/fix/handtools...skuId=11758762

It has an appreciably finer flame than the torch I use for soldering
pipes, so I'm hopeful it will do the trick for brazing. I don't think
I'll do any better without oxy setup which is too much for my modest
requirements.

A Mapp gas torch might be a better bet...


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Stephen wrote:

The Chemistry teacher held a lesson demonstrating the reactivity of
various metals such as sodium, potassium, phosphorus, Magnesium, lithium
etc.

Quest have just this week shown a Mythbusters episode featuring a
few interesting reactions in water.

Chris
--
Chris J Dixon Nottingham UK


Plant amazing Acers.

In article , Stephen wrote:
On 29/04/2014 21:51, Cursitor Doom wrote:

Have to admit I did notice lithium was a bit on the volatile side when
a teacher I once knew dropped a knob of it in a beaker of water,
blowing it to bits.
[...]
They stole the phosphorus from the lab. Phosphorus is so reactive its
kept under oil within its container.

http://www.bsac.com/divelocations.as...51&itemid=1923
"Divers are warned that white phosphorous is frequently found on world war
one vintage wrecks! In recent years a number of divers have been burned by
raising this dangerous substance to the surface where it can spontaneously
ignite when exposed to air."

(It oozes out of corroded shells. Curious divers get it on their hands.)