Thermite Welding

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Model T Ford Forum: Forum 2013: Thermite Welding
Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Driscoll on Saturday, March 09, 2013 - 06:59 pm:

After watching a railroad crew weld a couple of rails together using Thermite, I thought it would be handy to have some of that stuff around to make some quick repairs around the farm. It might be better than baling wire or duct tape. Has any body had any experience with Thermite?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Saturday, March 09, 2013 - 07:46 pm:

When I first glanced at the title I read it as "Termite Wedding"! :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Matthew David Maiers on Saturday, March 09, 2013 - 07:55 pm:

i seem to remember seeing a recipe for it, stuff gets pretty hot...

i think it would be pretty difficut to get everything setup right to weld with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gene Carrothers Huntington Beach on Saturday, March 09, 2013 - 07:59 pm:

Yes I been around this type of welding for attaching electrical grounds. It's sort of scary cause once you start the burning those no control until it burns out.
You have to be very careful where and how you store it.

When I've seen it used you had to have a fixture clamped on the beam with a containment for the powder.

I'm trying to think of a farm emergency job and a battery with leads may be better suited. Others may have more experience. How it anything be better than the old stand-by of baling wire / duct tape?

Good Luck and Be Careful


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike D, Williamsburg VA on Saturday, March 09, 2013 - 08:00 pm:

In my business we do some "cad welding"..welding copper conductors to ground rods and building steel.
I never heard of "Thermite Welding" so I looked it up
It's much like cad welding
"THERMITE WELDING (TW) is a fusion welding process in which two metals become bonded after being heated by superheated metal that has experienced an aluminothermic reaction. The liquid metal that results from the reaction between a metal oxide and aluminum acts as the filler metal. This exothermic process was discovered in 1898, in Germany, by Dr. Hans Goldschmidt of Goldschmidt AG. In the United States, this process was used in the early 1920s to join trolley car track. In 1933, thermite welding was used on the Delaware and Hudson Railroad at Albany, NY to produce long rail sections. In 1938, a researcher at the Electric Railway Improvement Company invented a copper-base aluminothermic process for welding copper conductors to steel rails. Currently, thermite welding is widely used in the field welding of track, where its portability and versatility are strong assets. It should be noted that the standard term for this process is often listed as “thermit” welding."


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Saturday, March 09, 2013 - 08:02 pm:

Zowie. The guys in the Thing From Another World destroyed a space ship with Thermite. Couldn't put it out either.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Saturday, March 09, 2013 - 08:17 pm:

You can get a book on the subject here :

http://www.youroldtimebookstore.com/product-p/23845.htm

Be_Zero_Be


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wes Nelson ........Bucyrus, MO on Saturday, March 09, 2013 - 08:31 pm:

Thermite welding rails

http://www.youtube.com/watch?v=5uxsFglz2ig


Top of pagePrevious messageNext messageBottom of page Link to this message  By ex trooper on Saturday, March 09, 2013 - 08:42 pm:

""Zowie. The guys in the Thing From Another World destroyed a space ship with Thermite. Couldn't put it out either.""

troop





https://www.youtube.com/watch?v=dRr5d4Q5vTc&list=PLE07778B49B868FD0


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Saturday, March 09, 2013 - 10:38 pm:

i often thought about repairing cars with thermite but it is mighty hard to get.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Floyd Voie - Chehalis, Washington on Sunday, March 10, 2013 - 12:47 am:

Randy, I don't know what it could be used for around the farm as it must have a crucible to contain the molten metal that is a result of the powder being lit. There are two powders, one being the ignition powder and one the metal powder.
Like Gene I have used thousands of these "Cadwelds" (brand name) over the years to weld wires to ground rods and to weld "bond wires"
to rail ends.
It is also critical to have the crucible moisture free or the weld material will blow out!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison_Rice Minnesota on Sunday, March 10, 2013 - 01:06 am:

All this reminds me of working with magnesium for a couple years. We had a fire start in one of our CNC lathes and weren't able to get it out quick enough and burnt the machine to the ground. We must have thrown a ton of powder in that machine. What a mess. Every year we had to go through training put on by the fire department on how to deal with magnesium fires. We'd go out in the parking lot and light a fire and then we'd throw water on it to watch it go crazy and flare up. The only way we could put that crap out was to put powder on it and let it sit. We'd knock down the flames and then wait until the magnesium completely burned itself away before we could uncover it. Then there were those that use to steal the machining chips and bring it home for their 4th of July parties.


Top of pagePrevious messageNext messageBottom of page Link to this message  By A. J. "Art" Bell on Sunday, March 10, 2013 - 04:01 am:

Cadweld (and Caddy Fasteners) are divisions of Erico Inc. based in Solon, Ohio.
Each Cadweld connection requires a reusable swing open carbon mold to hold the
charge and position the connection.
A plug is inserted in the bottom of the cavity, and it melts when the charge reaches
the correct temperature. This allows the molten metal to run into the mold to complete
the weld. Every thing from small ground cables on chain link fence to huge bus bars
for aluminum smelters have been connected with it. Interestingly it takes a spark to get
things going, a flame will not work. A good friend just retired as district manager for
N.W. US and Canada – pity, it means no more free Caddy and Cadweld ball caps for me.
Every where I wear them, chances are someone will recognize the product.
I don’t dare go near a golf course though <@^@>



Regards
Art


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Sunday, March 10, 2013 - 04:22 am:

(slight thread drift here) Does a magnesium casting furnace have to be sealed and filled with nitrogen?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Olsen on Sunday, March 10, 2013 - 04:23 pm:

We usually make our own thermite. As for storage, use a paint can. We use magnesium ribbon to start it burning. That is all it does, burn. The result is a lot of smoke (aluminum oxide) and iron. Most we ever did was about a ton and a half. Looked like a volcano. It was too hot to be closer than about a hundred feet.

As for magnesium, yeah it can be tough to put out. We have class D extinguishers at work for putting out Lithium and caesium out.
Remember the extinguisher classes:
A: any thing that makes Ash (wood/paper)
B: any thing in a Barrel (liquid)
C: any thing that ha Current(electrical)
D: Damn that's hot!


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare - Just a little South West . on Sunday, March 10, 2013 - 07:47 pm:

termite wedding here too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dare - Just a little South West . on Sunday, March 10, 2013 - 07:50 pm:

I think l watched a tv special about the welding/repairing of rail tracks in the north west of Australia ( the mining route ), where the track men would set up a small container over the track repair areas, light it up and off she'd go, a repair that you'd never know was done, didn't take long either.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Randy Driscoll on Sunday, March 10, 2013 - 07:59 pm:

Every year farming equipment gets bigger. We are always welding on chisel plow and disk frames. A broken harvester means a bunch of men standing around and nothing getting done. About half of our welding repair work is done in the field because either the piece can't be moved or we can do just as good a job laying in the dirt as laying on a creeper. When big iron breaks it has to be V'd out and multiple welding passes made. These are the cases where I thought thermite could come in handy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By P. Jamison on Sunday, March 10, 2013 - 08:16 pm:

Here's how they use it on the rails. I wonder how many welds they use. Perhaps the track sections are very long.

http://youtu.be/5uxsFglz2ig


Phil


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Sunday, March 10, 2013 - 11:23 pm:

In the field old fireclay around the crack and thermite welding would be very handy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Cole ---- Earth on Monday, March 11, 2013 - 12:48 am:

That is a amazeing process.Works quick to.
I have watched it a few times as I had to close roads when rails broke at crossings so traffic was directed away from them.
Once the railroad called us to close a road I was able to useally wait a while and then pull the detour right back out.The crews were there quick,and removal and replacement of the rail was done in minutes.I dont see how they do it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Garrison_Rice Minnesota on Monday, March 11, 2013 - 02:34 pm:

Kep NZ, interesting question regarding Magnesium. The company I worked for did magnesium diecasting. I use to watch them put billets of magnesium in the furnaces and the furnaces were kept closed. But I can't remember them having the magnesium in a nitrogen atmosphere.


Top of pagePrevious messageNext messageBottom of page Link to this message  By p.v.chowdary on Sunday, October 27, 2013 - 12:21 pm:

Subject: Improved method of Alumino Thermit Welding of railway rails -- Dissemination of the latest knowledge--Request regarding.
As a dedicated scientist and researcher that worked for NINE long years, I personally request to please disseminate the latest developments in Alumino Thermit Welding of railway rails. Thanks in advance.
Improved method of alumino thermit welding of railway rails in which defect formation during execution of welding is retarded and thereby endurance limit and fatigue resistance of weldment are improved.
The 'Fatigue Strength' of Alumino Thermit welding of railway rails has been a matter of concern for all the railway industry. Alumino thermit welding is a great technique which does not need rail movement [no forging step] during the execution of welding. But its low fatigue resistance has been haunting the railway industry of the globe. A lot of research has been done by researchers all over the world for more than 15 years to improve the fatigue resistance of Alumino Thermit welding of railway rails.
I spent more than 9 years of my life for experimenting and researching for improving the fatigue resistance of Alumino Thermit welding of railway rails. I could develop three improved techniques that can give Alumino Thermit weldings that have fatigue strength at par with 'Electric Flash Butt welding' of railway rails.
The details of those three techniques are given below:
1. CHOWDARY-TECHNIQUE-1 : -
Abstract:
“Preventing or reducing defects” improves ‘endurance limit’ and ‘fatigue resistance’ of alumino thermit welding of railway rails.
“Thermal insulation of two rails on both sides of mould up to one meter length on each side starting from mould wall” retards dissipation of “heat energy that conducts to two rails from weld cavity’ into ambient air via surfaces of ‘heat dissipating zones’ of two rails and retains heat energy in two rails.
Retention of heat energy in the two rails causes:
a) Prevents thermal contraction of “heated and thermally expanded regions of two rails” during ‘solidification phase of welding’ and thereby prevents occurrence of ‘tearing apart tensile stresses’ and thereby prevents ‘hot tearing’ and formation of ‘centerline defect’;
b) Reduces thermal gradient and thereby reduces conductive heat flux from weld cavity to two rails and thereby:
i) Causes ‘increase in depth of melt-back of stick-out rail ends’, which prevents ‘cold-lap defect formation’,
ii) Demotes ‘progression of parallel dendritic solidification fronts of rails 51 and 52 towards each other along longitudinal axis of rails’, which prevents formation of liquid weld metal pool locked amidst nascent solidus and thereby prevents ‘shrinkage cavity defect formation’,
iii) Reduces criticality of ‘initial temperature of superhot thermite liquid metal tapped into weld cavity’ and thereby reduces quantity of dissolved gases in thermite liquid metal, which reduces severity of ‘microporosity defect’.
c) during solidification phase of welding increases conductive heat flux to the bottom of mould due to dissipation of heat energy via surfaces of heat dissipating fins present at the bottom of mould-assembly and thereby promotes vertically upward directional solidification of fused liquid metal present in weld-cavity and thereby prevents shrinkage cavity defect formation.
SUMMARY OF INVENTION
Defects are discontinuities in the solid core of weldment and act as stress concentrators. Due to ‘stress concentration effect’, defects cause to diminish the value of ‘endurance limit’ and ‘fatigue resistance’ of weldment. This invention optimizes heat flux characteristics of weldment and thereby prevents those defects that are preventable and reduces severity of those defects that are not preventable” and thereby improves endurance limit and fatigue resistance of weldment.
This invention is implemented as follows:
1. Mould-assembly that has ‘heat dissipating fins’ at the bottom is used. In case of a 2-piece mould, metallic ‘heat-dissipating fins’ are welded to the bottom surfaces of ‘two pieces of metallic mould protector’. In case of a 3-piece mould, metallic ‘heat-dissipating fins’ are welded to the bottom surface of metal plate that supports bottom briquette of a 3-piece mould.
2. During ‘melt-back and fusion phase’ of welding:
(i)The surface of ‘heat dissipating zones’ of two rails that are open into ambient air are covered with thermal insulating sleeves up to one meter each starting from mould wall on both sides of mould,
(ii) The ‘heat-dissipating fins’ present at bottom of welding are covered with ‘thermal insulating basket sleeve’,
According to Fourier’s law of conductive heat flux, the time rate of heat transfer through a material is proportional to the negative gradient in the temperature through which the heat is flowing.

where, is the local heat flux, 1 is the rail steel’s conductivity and is the temperature gradient.
Thermal conductivity of rail steel varies a little with temperature. Since, this variation is small, thermal conductivity, 1 , of rail steel can be taken as a constant. Similarly, for the bottom of sand mould also, the value of thermal conductivity, 2, can be taken as constant. Therefore, by decreasing temperature gradient, conductive heat flux from weld cavity to the two rails as well as to the heat dissipating fins present at bottom of mould-assembly via thin bottom of sand-mould reduces.
(iii) During tapping time, the openings of two side-riser cavities are plugged with two circular sand-plugs numbered as 82 as shown in figures 14 and 15.
3. During solidification phase of welding:
(i) Thermal insulation to the web regions and head regions of heat dissipating zones of two rails is kept until the completion of solidification of fused liquid metal present in weld-cavity,
(ii) Two small pieces of thermal insulating pads present at the bottom surface of two rails just beside mould wall on both sides of mould are removed to allow dissipation of heat energy via bottom surfaces of regions of two rails present just beside mould-wall on both sides of mould,
(iii) The ‘thermal insulating basket sleeve’ that covers ‘heat dissipating fins’ present at the bottom of mould is removed without disturbing the mould or welding set-up and thereby allows dissipation of heat energy via surfaces of ‘heat dissipating fins,
(iv) Compressed air or ambient air is blown up on the ‘heat dissipating fins’ and on the bottom surfaces of two rails just beside mould wall present on both sides of mould to promote convection transfer of heat energy.
This invention optimizes the heat flux characteristics of weldment during execution of welding as summarized below:
1. During ‘melt-back phase of welding’, conductive heat flux from weld cavity to ‘two rails present on both sides of it’ and to ‘the heat dissipating fins present at the bottom of mould’ is reduced by reducing temperature gradient,
2. Immediately after stopping pre-heating process, during the start of span of tapping time, two circular sand-plugs are placed up on the two openings of riser cavities to stop convectional transfer heat energy because of passage of hot air from riser cavity in to ambient air,
3. During ‘solidification phase of welding’ also, conductive heat flux from weld-cavity to ‘the web regions and head regions of two rails’ present on both sides of it is reduced by reducing temperature gradient due to retarding of dissipation of heat energy into ambient air by thermal insulating sleeves,
4. During ‘solidification phase of welding’, conductive heat flux from weld-cavity to the bottom of mould is increased by increasing temperature gradient, due to dissipation of heat energy into ambient air via surfaces of ‘heat dissipating fins’ because of convectional transfer of heat energy due to blowing air,
5. During ‘solidification phase of welding’, conductive heat flux from weld-cavity to the foot regions of two rails is increase by allowing dissipation of heat energy into ambient air via spaces 71 and 72 present at the bottom surfaces of two rails just beside mould wall on both sides of mould.
Thus, by controlling temperature gradient characteristics, this invention optimizes heat flux characteristics of weldment and retards occurrence conditions of defects as explained below:
(i) Prevents thermal contraction of ‘heated and thermally expanded regions of two rails present on both sides of weld-cavity’ and thereby prevents ‘tearing apart tensile stresses’ that tend to tear apart nascent solidus-bridge of weld-collar in opposite directions and thereby prevents ‘hot tears defect’ formation and ‘centerline defect’ formation,
(ii) During ‘melt-back phase’ of welding, reduces conductive heat flux from weld-cavity and thereby retains comparatively more quantity of heat energy weld-cavity and in stick-out rail ends and thereby increases depth of ‘melt-back and fusion of stick-out rail ends of weld-cavity’. Thereby prevents ‘cold-lap defect’ formation,
(iii) During ‘solidification phase’ of welding, demotes horizontal plane (or longitudinal axis) progression of parallel progressive dendritic solidification fronts of solid-liquid interfaces of two rails because of reduced conductive heat flux to the two rails from weld-cavity. Thereby contributes to prevent liquid weld metal pool formation and thereby prevents ‘shrinkage cavity defect’ formation,
(iv) During ‘solidification phase’ of welding, promotes ‘vertically upward directional solidification of fused liquid metal present in weld-cavity’ because of an increase in conductive heat flux from weld-cavity to the ‘heat dissipating fins’ present at the bottom of ‘mould-assembly’. Thereby prevents formation of liquid weld metal pool locked amidst nascent solidus and thereby prevents shrinkage cavity defect formation,
(v) Reduces criticality of quantity of input heat energy into weld-cavity for achieving proper fusion and thereby decreases quantity of dissolved gases in fused liquid metal present in weld-cavity.
2. CHOWDARY-TECHNIQUE-2:-
Abstract:
“Preventing or reducing defects” improves ‘endurance limit’ and ‘fatigue resistance’ of alumino thermit welding of railway rails.
The regions of two rails present just beside mould wall on both sides of mould are heated to a temperature between 200o C to 1200o C, preferably between 500o C to 900o C using any heat energy sources like burners that are used in gas-pressure welding in time span between start of pre-heating process up to completion of solidification of weld collar.
Heating of regions of two rails just beside mould wall to a high temperature causes:
a) Prevents thermal contraction of “heated and thermally expanded regions of two rails” during ‘solidification phase of welding’ and thereby prevents occurrence of ‘tearing apart tensile stresses’ and thereby prevents ‘hot tearing’ and formation of ‘centerline defect’;
b) Reduces thermal gradient and thereby reduces conductive heat flux from weld cavity to two rails and thereby:
i) Causes ‘increase in depth of melt-back of stick-out rail ends’, which prevents ‘cold-lap defect formation’,
ii) Demotes ‘progression of parallel dendritic solidification fronts of rails 41 and 42 towards each other along longitudinal axis of rails’, which prevents formation of liquid weld metal pool locked amidst nascent solidus and thereby prevents ‘shrinkage cavity defect formation’,
iii) Reduces criticality of ‘quantity of heat energy that is tapped into weld-cavity’ for achieving proper fusion and thereby reduces quantity of dissolved gases in fused liquid metal present in weld-cavity and thereby reduces severity of microporosity defect.
c) during solidification phase of welding increases conductive heat flux to the bottom of mould due to dissipation of heat energy via surfaces of heat dissipating fins present at the bottom of mould-assembly and thereby promotes vertically upward directional solidification of fused liquid metal present in weld-cavity and thereby prevents shrinkage cavity defect formation.
SUMMARY OF INVENTION
Defects are discontinuities in the solid core of weldment and act as stress concentrators. Due to ‘stress concentration effect’, defects cause to diminish the value of ‘endurance limit’ and ‘fatigue resistance’ of weldment. This invention optimizes heat flux characteristics of weldment and thereby prevents those defects that are preventable and reduces severity of those defects that are not preventable” and thereby improves endurance limit and fatigue resistance of weldment.
This invention is implemented as follows:
1. Two burners resembling burners that are used in gas-pressure welding of railway rails shown as 43 and 44 in figure 1 are placed on both sides of mould, just beside mould wall.
2. Mould-assembly that has ‘heat dissipating fins’ at the bottom is used. In case of a 2-piece mould, metallic ‘heat-dissipating fins’ are welded to the bottom surfaces of ‘two pieces of metallic mould protector’. In case of a 3-piece mould, metallic ‘heat-dissipating fins’ are welded to the bottom surface of metal plate that supports bottom sand-briquette of a 3-piece mould.
3. During ‘melt-back and fusion phase’ of welding, at the start of pre-heating process, the below regions are heated:
(i) The two regions of rails 41 and 42 beneath the burners 43 and 44, which are denoted as 115 and 116 shown in figure 19 and figure 20 are heated to a temperature anywhere between 200o C to 1200o C, preferably between 500o C to 900o C.
(ii) ‘Heat dissipating fins’ present beneath the mould-assembly are also heated with the help of burners up to a temperature of 200o C to 1200o C, preferably between 500o C to 1200o C.
According to Fourier’s law of conductive heat flux, the time rate of heat transfer through a material is proportional to the negative gradient in the temperature through which the heat is flowing.
where, is the local heat flux, is the rail steel’s thermal conductivity, and is the temperature gradient.
Thermal conductivity of rail steel varies a little with temperature. Since, this variation is small, thermal conductivity, 1, of rail steel can be taken as a constant. Similarly for the bottom of sand mould also, the value of thermal conductivity, 2 can be taken as constant.
Therefore, by decreasing temperature gradient, conductive heat flux from weld cavity to the two rails as well as to the heat dissipating fins present at bottom of mould-assembly via thin bottom of sand-mould reduces.
(iii) During tapping time, the openings of two side risers cavities are plugged with two circular sand plugs numbered as 61 as shown in figures 6 and 7.
4. During solidification phase of welding:
(i) The two burners that heat up the regions of two rails present just beside mould wall on both sides of mould are continuously burnt,
(ii) The burners that heat up ‘heat dissipating fins’ present at the bottom of mould-assembly are stopped and
(iii) Compressed air or ambient air is blown up on the ‘heat dissipating fins’ present at the bottom of mould-assembly to promote convection transfer of heat energy.
This invention optimizes the heat flux characteristics of weldment during execution of welding as summarized below:
1. During ‘melt-back phase of welding’, conductive heat flux from weld cavity to (a) ‘two rails present on both sides of it’, and (b) ‘the heat dissipating fins present at the bottom of mould-assembly’ is reduced by reducing temperature gradient,
2. During the span of tapping time, the convectional heat transfer by passage of hot air is plugged by the two circular sand-plugs,
3. During ‘solidification phase of welding’, conductive heat flux from weld-cavity to the two rails 41 and 42 present on both sides of it is reduced by continuously burning the burners and thereby reducing temperature gradient,
4. During ‘solidification phase of welding’, conductive heat flux from weld-cavity to the bottom of mould-assembly is increased by increasing rate of dissipation of heat energy into ambient air by i) stopping supply of heat energy to the ‘heat dissipating fins’ and then ii) blowing air onto the ‘heat dissipating fins’ and thereby increasing temperature gradient.
Thus, by controlling temperature gradient characteristics, this invention optimizes heat flux characteristics of weldment and retards occurrence conditions of defects as explained below:
(i) The two burners continuously supply heat energy to the regions of two rails present beside mould wall on both sides of mould and thereby prevent thermal contraction of ‘heated and thermally expanded regions of two rails present on both sides of weld-cavity’ and thereby prevents ‘hot tears defect’ formation and ‘centerline defect’ formation,
(ii) Reduces conductive heat flux from weld-cavity and thereby increases ‘depth of melt-back and fusion of stick-out rail ends of weld-cavity’. Thereby prevents ‘cold-lap defect’ formation,
(iii) Demotes horizontal plane (or longitudinal axis) progression of parallel progressive dendritic solidification fronts of solid-liquid interfaces of two rails. Thereby prevents liquid weld metal pool formation and thereby prevents ‘shrinkage cavity defect’ formation,
(iv) Promotes ‘vertically upward directional solidification of fused liquid metal present in weld-cavity’ because of dissipation of heat energy via surfaces of ‘heat dissipating zones present at the bottom of mould-assembly’
(v) Reduces criticality of quantity of input heat energy put into weld-cavity and thereby decreases quantity of dissolved gases in fused liquid metal present in weld-cavity and thereby reduces severity of ‘microporosity defect’
3. CHOWDARY-TECHNIQUE-3: -
Abstract:
“Preventing or reducing defects” improves ‘endurance limit’ and ‘fatigue resistance’ of alumino thermit welding of railway rails.
The regions of two rails present just beside mould wall on both sides of mould are heated to a temperature between 200o C to 1200o C, preferably between 500o C to 900o C using two phase-burners during melt-back phase of welding. Similarly, heat dissipating fins are heated to a temperature 200o C to 1200o C, preferably between 500o C to 900o C during melt-back phase of welding.
Heating of regions of two rails just beside mould wall to a high temperature causes:
a) Reduces thermal gradient and thereby reduces conductive heat flux from weld cavity to two rails and thereby:
i) Causes ‘increase in depth of melt-back of stick-out rail ends’, which prevents ‘cold-lap defect formation’,
ii) Reduces criticality of ‘quantity of heat energy that is tapped into weld-cavity’ for achieving proper fusion and thereby reduces quantity of dissolved gases in fused liquid metal present in weld-cavity and thereby reduces severity of microporosity defect.

b) during solidification phase of welding, the flames of two phased burners are utilized to control conductive heat flux from weld-cavity to various regions of two rails. Thereby, solidification pattern of fused liquid metal present in weld-cavity is controlled in such a way to promote vertically upward directional solidification.

c) during solidification phase of welding increases conductive heat flux to the bottom of mould due to dissipation of heat energy via surfaces of heat dissipating fins present at the bottom of mould-assembly and thereby promotes vertically upward directional solidification of fused liquid metal present in weld-cavity and thereby prevents shrinkage cavity defect formation.
SUMMARY OF INVENTION
Defects are discontinuities in the solid core of weldment and act as stress concentrators. Due to ‘stress concentration effect’, defects cause to diminish the value of ‘endurance limit’ and ‘fatigue resistance’ of weldment. This invention optimizes heat flux characteristics of weldment and thereby prevents those defects that are preventable and reduces severity of those defects that are not preventable” and thereby improves endurance limit and fatigue resistance of weldment.
This invention is implemented as follows:
1. Two ‘phased-burners’ that have separate fuel supply pipelines for various zones of flames, as shown in figures 4, 5, 6, 7 and 8 are placed on both sides of mould just beside mould wall as shown in figure 1.
2. Two burners resembling burners that are used in gas-pressure welding of railway rails shown as 55 and 56 in figure 1 are placed on both sides of mould at a distance of about 50 centimeters to the two ‘phased-burners’ 53 and 54.
3. Mould-assembly that has ‘heat dissipating fins’ at the bottom is used. In case of a 2-piece mould, metallic ‘heat-dissipating fins’ are welded to the bottom surfaces of ‘two pieces of metallic mould protector’. In case of a 3-piece mould, metallic ‘heat-dissipating fins’ are welded to the bottom surface of metal plate that supports bottom briquette of a 3-piece mould.
4. During ‘melt-back and fusion phase’ of welding, at the start of pre-heating process, the below regions are heated:
(i) The two regions of rails 51 and 52 beneath the burners 53 and 54 are denoted as 151 and 152 are heated to a temperature anywhere between 200o C to 1200o C, preferably between 500o C to 900o C.
(ii) ‘Heat dissipating fins’ present beneath the mould-assembly are heated with the help of burners up to a temperature of 200o C to 1200o C, preferably between 500o C to 900o C.
According to Fourier’s law of conductive heat flux, the time rate of heat transfer through a material is proportional to the negative gradient in the temperature through which the heat is flowing.
where , is the local heat flux, is the rail steel’s thermal conductivity, and is the temperature gradient.
Thermal conductivity of rail steel varies a little with temperature. Since, this variation is small, thermal conductivity, , of rail steel can be taken as a constant.
Therefore, by decreasing temperature gradient, conductive heat flux from weld cavity to the two rails as well as to the heat dissipating fins present at bottom of mould via bottom of sand mould reduces.
5. During solidification phase of welding:
(i) The flames of different regions of two ‘phased-burners’ that heat up the regions of two rails present just beside mould wall on both sides of mould are put-off in a phased manner, starting from the foot region, then putting-off flames of web region and finally flames of head region,
(ii) The burners that heat up ‘heat dissipating fins’ present at the bottom of mould-assembly are stopped,
(iii) Compressed air or ambient air is blown up on the ‘heat dissipating fins’ present at the bottom of mould-assembly to promote convection transfer of heat energy and
(iv) The two normal-burners 55 and 56 are put-on and continued till the process of vertically upward solidification of fused liquid metal of weld-cavity is complete up to the head region.
This invention optimizes the heat flux characteristics of weldment during execution of welding as summarized below:
1. During ‘melt-back phase of welding’, conductive heat flux from weld cavity to (a) ‘two rails present on both sides of it’, and (b) ‘the heat dissipating fins present at the bottom of mould-assembly’ is reduced by reducing temperature gradient,
2. During ‘solidification phase of welding’, conductive heat flux from weld-cavity to foot regions, web regions and head regions of two rails present on both sides of it is increased by putting-off flames corresponding to various zones in a phased-manner and thereby solidification pattern of fused liquid metal is controlled in such a way to promote vertically upward directional solidification of fused liquid metal of weld-cavity.
3. During ‘solidification phase of welding’, conductive heat flux from weld-cavity to the bottom of mould-assembly is increased by increasing rate of dissipation of heat energy by blowing compressed air or ambient air and thereby increasing temperature gradient and conductive heat flux,
4. During solidification phase of welding flames of the two normal-burners 55 and 56 are put-on and thereby supply heat energy to 153 and 154 regions of two rails and thereby cause thermal expansion of these two regions and thereby compensate thermal contraction volume shrinkage of 151 and 152 regions of two rails and thereby preventing occurrence of ‘tearing apart tensile stresses’ that tend to tear apart nascent solidus-bridge that forms at the foot region of weld-cavity in opposite directions.
Thus, by controlling temperature gradient characteristics, this invention optimizes heat flux characteristics of weldment and retards occurrence conditions of defects as explained below:
(i) During ‘melt-back and fusion phase of welding’, the two ‘phased-burners’ supply heat energy to the regions 151 and 152 of two rails present beside mould wall on both sides of mould and thereby reduces conductive heat flux from weld-cavity and thereby increases ‘depth of melt-back and fusion of stick-out rail ends of weld-cavity’. Thereby prevents ‘cold-lap defect’ formation,
(ii) Demotes horizontal plane (or longitudinal axis) progression of parallel progressive dendritic solidification fronts of web regions and head regions of two solid-liquid interfaces of two rails by putting-off flames at foot regions and keeping flames of web regions and head regions of the two ‘Phased-burners’. Thereby promotes ‘vertically upward directional solidification of fused liquid metal present in weld-cavity’ and thereby contributes to prevent liquid weld metal pool formation and thereby prevents ‘shrinkage cavity defect’ formation,
(iii) Promotes dissipation of heat energy via surfaces of ‘heat dissipating fins’ present at the bottom of mould-assembly and thereby contributes to promote ‘vertically upward directional solidification of fused liquid metal present in weld-cavity’ thereby contributes to prevent liquid weld metal pool formation and thereby prevents ‘shrinkage cavity defect’ formation,

(iv) Compensates thermal contraction of 151 and 152 regions of two rails by thermally expanding 153 and 154 regions of two rails and thereby prevents occurrence of ‘tearing apart tensile stresses’ which tend to tear apart the nascent solidus-bridge formed in between the two solid-liquid interfaces of two rails and thereby prevents ‘hot tears defect’ formation and ‘centerline defect’ formation,

(v) Reduces criticality of quantity of input heat energy put into weld-cavity and thereby decreases quantity of dissolved gases in fused liquid metal present in weld-cavity and thereby reduces severity of ‘microporosity defect’

Because of many requests for ‘DRAWINGS of the three PATENT SPECIFICATIONS’, an attachment of ZIP file containing drawings of patent specifications is attached with this letter.
Yours Sincerely,
P.V.Chowdary.



From:
P.V.Chowdary,
# 86-5-2/4,
2nd Street, Manthena Gardens,
J.N.Road,
RAJAHMUNDRY--533 103,
Andhra Pradesh,
INDIA.

Ph. : +91 81 2151 7555

e-mail: pvchowdary9@gmail.com


Top of pagePrevious messageNext messageBottom of page Link to this message  By Will Copeland - Trenton, New Jersey on Sunday, October 27, 2013 - 12:28 pm:

Back in my Army days we trained using thermite to destroy enemy weapons so they could not be used again. You could render a cannon or an armored vehicle useless in just seconds


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Sunday, October 27, 2013 - 02:23 pm:

Thermite is very nasty stuff. It will render most metal items useless - that means "burn a big hole right thru it". Like Floyd, I've used it through an entire railroad career and have watched crews weld rails together with it, and it demands respect. It also makes for a large mess and headache when the moulds leak unintentionally. For any personal use one would have to be quite skilled in making up their own sand or graphite moulds. If you want to make a big kaboom just put some on dry ice as seen on youtube. I would warn against doing so unless you have a local bunker. You can't outrun a molten thermite explosion!

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Wolf on Sunday, October 27, 2013 - 04:14 pm:

Has anyone taken the time to read pvchowdary's post?????????


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, October 28, 2013 - 02:37 am:

I found it to be a most interesting read. It crosses the boundaries between science, art, and invention. Broken into three sections, with only minor differences in focus, each section split into two parts restating much of what had previously been said, only from a slightly different angle.
I do wish the illustrations referenced to were included here, however, our (okay I will say it) archaic web site probably couldn't print them as presented.
Actually, very interesting. And yes, I read every word.
I question the patent-ability and marketability of all this, however, it would seem to be a potentially valuable improvement over previous thermite welding methods. Then again, since I have no practical background with thermite for any purpose other than theoretical and curiosity, I do not know just how different his process is from common thermite practice.
Makes me want to experiment a bit. Don't worry. I probably won't. And with a lot of practical experience with electricity, and working on communication towers, and welding, and underground construction (shall I go on) etc. I do know how to respect things that can get very bad very fast. I still have all my fingers and toes. However a few scars.
Anyway. This may not have been the most appropriate place for him to post his findings, but I found it interesting. He most likely "Googled" thermite and posted his piece in a lot of places.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Zachary Dillinger on Monday, October 28, 2013 - 09:49 am:

On a tv show once they made thermite by grinding up some pop cans and putting into plaster of paris with a fuse stuck in it. Somehow I doubt that is the "real" recipe, but I always wanted to try it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By p.v.chowdary on Saturday, November 02, 2013 - 06:38 am:

Thank you all for encouraging response and appreciation. With your encouragement, I could forget all the nine years of hardships I faced in experimenting, researching and inventing the three techniques for ‘improving the fatigue resistance of alumino thermit weldings of railway rails’.

Because of many ‘personal requests’ for the drawings of the three improved techniques of alumino thermit welding of railway rails, I am herewith giving the web-link below to download the 'drawings as well as the three Complete Specifications' from ‘google-drive’. . . . . . . . . . Thank you all again. . . . . . . . . . . P.V.Chowdary.


https://docs.google.com/file/d/0B75r3Av994ywTHVDd2NlV1J1dXM/edit?usp=drive_web


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