Making a field weld is serious business.
And while our headline pokes a bit of fun at the danger of making a field weld on the railroad, we remind ourselves that SAFETY COMES FIRST.
Safety Comes First.
That’s because we’re working with small batches of molten steel in an on-site environment.
We’re talking serious heat, volatile materials and very specific protocols in an impromptu location.
These little bowls of fun are produced by Railtech Boutet (pronounced “boo-tay” – go ahead and laugh, but it’s a great company with headquarters in France).
These flash pots require a lot of forethought and planning and attention to detail.
For serious rail in the modern age, you want Continuous Welded Rail or CWR for short. CWR eliminates the joint bars in railroads that are used to connect up the 39-foot long sections rail typically comes in.
There are many advantages that we won’t go into depth about, but suffice to say that it removes a lot of the movement in tracks and helps mitigate many issues that degrade the quality of a track.
If you want the official guide to making a field weld from RailTech Boutet, you can find a link to their manual at the bottom of this post.
Step 1: Pack the Mold
Packing the mold is the most important step when it comes to quality of the pour. A poorly packed mold will fail and the molten steel will seep out and the weld will fail resulting in lost time and money.
Failing to put the plug in the bottom of the mold is an easy oversight, and that mistake will allow hot molten steel to run right through the weld and pour out the bottom of the mold – not the desired result.
A failed weld not only means the cost of the weld and the time spent setting up are lost, but also the rail can be damaged and new ends must be cut, rail must be shifted and a new weld prepared.
The next step is setting up the single use terra cotta pot that will hold the pellets that will be set alight. This glorified flower pot will serve as the crucible for the liquid steel and direct the flow of the molten alloy into the gap between the two rails.
Then it gets serious.
You light an aluminum fuse that gets dropped into the mixture.
Then you run like hell – well, at least you move quickly away, to be a little less dramatic about the whole thing.
Thermite: Ingredient in C-4
The mixture contains Thermite, an ingredient in military grade explosives like C-4, and in field welds.
Yes, this is serious stuff.
It gets hot very – quickly!
2384-degrees Fahrenheit to be specific.
The thermite and iron shot turn liquid with the heat, melting and flowing down through the mold to fill the gap between the two rails with the overflow running out into a pan designed to catch the molten steel.
After that the process gets a bit more tame.
We wait a bit and allow the molten steel to set up – but not too long before we knock the molds loose, and get back to work.
No Rest for the Railroader
It’s still hot – but cooling rapidly, so there’s no time to sit around.
The slag above the rail profile needs to be sheared off as cleanly as possible with the head of the rail with the rail shear attached to the Matweld – another product from RailTech Boutet (stop giggling).
The Matweld is a versatile hydraulic engine that operates multiple tools including the rail shear and the grinder which are a critical part of the field welding process.
The shear gets the weld off the top of the rail, then there’s the hand work of knocking off the outside of the rail profile with a hammer and steel wedge.
After that, it’s time to get the rail grinder out and clean up the edges of the weld to allow smooth transit of the wheels along the rails.
Sounds simple, and it’s very doable, but it takes a steady hand, a cool head and learning from some experienced folks to make sure it all goes according to plan.
Want the nitty gritty details on how this is done?
Check out the official Weld-Training Guide from RailTech Boutet (seriously, you’re still giggling?)
And then there is the exhaustive set of directions